In the original sound system design for the IBM PCjr., there could be four sources of audio, the 8253 Timer-driven PC Speaker, the 3 Voice TI SN 76496, the Cassette input or an adapter on the bus like the IBM PCjr. Speech Attachment Sidecar. IBM set aside two bits in the 8255 Programmable Peripheral Interface at I/O Port 61 to control a multiplexer which would determine the source to be used. The bits used were 5 & 6, and here is what they controlled :
Bit 6 Bit 5
0 0 PC Speaker (Default)
0 1 I/O Channel Audio In (PCjr. Speech Attachment)
1 0 Cassette Audio Input
1 1 TI SN76496 3 Voice
Pretty logical. An important point to note that this multiplexer only controlled the output to the external audio RCA output jack, the RF output connector or the PCjr. Monitor connector for an IBM 4863 PCjr. Display with built-in speaker. The PCjr.'s internal beeper would only output PC Speaker Audio, doubtless IBM felt it was too tinny for anything else.
When Tandy cloned the PCjr., this arrangement served them just fine for the Tandy 1000 with two exceptions. Since the 1000 did not support a cassette interface, the setting for the Cassette Audio Input sent nothing to the external audio RCA output jack. However, they decided to engineer the outputs very differently. The TI SN 76496 has an audio input pin which can mix an external audio source with the 3-voice sound the chip itself is producing. On the PCjr., this pin is unconnected. On the 1000, it is connected to the PC Speaker input. Then the mixed audio is sent to the internal speaker and to the multiplexer. Thus the bits operate as follows :
Bit 6 Bit 5
0 0 PC Speaker (Default)
0 1 I/O Channel Audio In
1 0 Nothing
1 1 PC Speaker + TI SN76496 3 Voice
No known device actually sent audio over the ISA bus, so the I/O Channel Audio In is effectively a "nothing" selection. The Tandy 1000 had a very large internal speaker, so the PC Speaker and 3-Voice sound is done justice. However, the internal speaker cannot be turned off without physically disconnecting it from the pins on the motherboard..
Thinking that inability to turn off the internal speaker was a bad thing, Tandy decided to make the multiplexer more complex in the SX and EX series. They added a third bit which is intended to turn the internal speaker off if set to 1. Tandy refers to these bits as follows :
SNDCTRL0 = Bit 5 of 8255 Port B / Connects to MC14529 Pin 6/"A"
SNDCTRL1 = Bit 6 of 8255 Port B / Connects to MC14529 Pin 7/"B"
SNDCTRL2 = Bit 4 of 8255 Port B / Connects to MC14529 Pin 15/"STy"
The internal outputs were thus made more complicated :
Bit 6 Bit 5 Bit 4 Internal External
0 0 0 PC Speaker + TI SN76496 3 Voice PC Speaker (Default)
1 0 0 PC Speaker + TI SN76496 3 Voice Nothing
0 1 0 I/O Channel Audio In I/O Channel Audio In
1 1 0 PC Speaker + TI SN76496 3 Voice PC Speaker + TI SN76496 3 Voice
0 0 1 Nothing PC Speaker
0 1 1 Nothing Nothing
1 0 1 Nothing I/O Channel Audio In
1 1 1 Nothing PC Speaker + TI SN76496 3 Voice
Thus if a program sets Bit 4, the best you would hear from the external speaker would be the PC Speaker sound. The SX's multiplexer is wired to have two outputs, one for the RCA jack and another for the internal speaker. The EX's multiplexer has only one output wired, and it goes to an earphone jack and the internal speaker. By default the audio is heard through the internal speaker, but plug in a mini-jack and the audio is switched to whatever is plugged into the jack, headphones or external speakers. However, the the portion of the multiplexer the EX uses is controlled by Bit 4, so if that bit is set you will have the same problem as on the SX. You will also have the same problem if a program sets bit Bit 5 without setting Bit 6. If Bit 6 is set without Bit 5, you will get no external audio output on the SX. The SX has a potentiometer inside the machine that can control the internal speaker's volume, but the EX has a volume wheel on the outside.
The HX, TX, TL, SL and later systems also have headphone jacks with external volume wheels. However, Bits 5 & 6 do nothing in the HX, and in the TX and the other systems bit 5 has no function while bit 6's function is completely different. Only bit 4 functions in these systems. In addition, I/O Channel Audio In is no longer supported.
Since I have an SX, I can discuss its multiplexing scheme. The default value for I/O port 61 on bootup is 08. This means that Bits 4-6 are 0. The external output will only output PC Speaker sound. This is generally not desirable, and Sierra's games will enable the external audio. After exiting from a Sierra game, the value for I/O port 61 is now 68. The program has set bits 5 & 6. LucasArts games will not enable the external audio output on the SX, so the simplest solution is to run a Sierra game before hand. There is a program called tdyspkr.com that will allow you to make settings designed for the SX or easily allow you to manipulate the bits yourself.
Showing posts with label Tandy 1000. Show all posts
Showing posts with label Tandy 1000. Show all posts
Sunday, June 2, 2013
Tandy 1000 Originals
I have often had occasion to blog about the Tandy 1000, but in terms of gaming, its importance is rather limited. I am a proponent of sticking to the original development system for a game. For example, practically every game published by Richard Garriott (before and with Origin) in the 1980s was developed on the Apple II. Most of the 1980s U.S. computer game developers cut their teeth one way or another on Cupertino's machine. His games really do not have a whole lot to offer on other systems. They don't take much advantage of the enhanced graphics and sound of the Atari 8-bit, ST, Commodore 64 or Amigas. Jordan Mechner's Karateka and Prince of Persia may look more colorful on other systems but play the same. For later games, FTL released their seminal dungeon-crawler classic Dungeon Master for the Atari ST and the game looks the same on the PC, even though it supports VGA. Sid Meier's Pirates! is a classic game that plays very well on its original platform, the Commodore 64. Not all games fall squarely into this category. Will Wright's SimCity began life on the Commodore 64, but by the time it was ported to 16-bit machines, it had gained many new features and functionality. Even so, it received Amiga and Macintosh releases before it was released on the PC.
Typically, the main advantage of the PC over every other platform is the prolific availability of hard drives, even (relatively) for the earliest machines, many speeds to choose from and a huge variety of clones to choose from. Who wants to put up with long load times, floppy swaps and inflexible system speeds? The earliest PC games would have been developed for the IBM PC, but most of those games were ports or otherwise historically unimportant and not usually rigidly wedded to IBM's hardware or the CPU speed.
The first historically significant PC game that was released and was not a port was King's Quest. This of course was originally released for the IBM PCjr. The PC version was released soon after and Tandy 1000 version would have been in existence by 1985. The Tandy 1000 version is nearly identical with the PCjr. version. King's Quest II came in one version with support for all three architectures, PC, PCjr. and Tandy 1000. However, it is clear that of these three systems, the best one to play any of Sierra's AGI games is the Tandy 1000. Not only do you get the enhanced graphics and sound, you do not incur the performance penalty of running the first 128K of the PCjr. on the Tandy 1000.
Thus is my definition of a "Tandy Original". First, it must not have been originally developed or released for a non-PC system. No ports from an Apple machine or Atari or Commodore non-IBM PC compatible. Second, the game supports the Tandy Graphics Adapter but no EGA or VGA support, or in the alternative the game supports the Tandy Sound Chip but has no Adlib, Sound Blaster, Roland MT-32 or other sound device support beyond the PC Speaker.
Thus for the AGI-engine games after King's Quest, they were probably developed mostly on Tandy and PC systems. Even King's Quest probably had more work done on it on the PC than on the PCjr. due to the not-insignificant advantages for the PC. When the hard drive installable versions of the games were released, starting with King's Quest III and Space Quest, these were easy to do on the Tandy 1000 and PC compatibles. Since hard drives were an expensive third-party add-on for the PCjr., fewer of these systems enjoyed this feature. I classify all the AGI engine-games as Tandy 1000 originals with two exceptions : King's Quest IV, which was developed for the SCI system and supported much more advanced sound hardware than the Tandy chip and Donald Duck's Playground, which was originally a non-AGI Commodore 64 game.
None of the other games Sierra released during the mid-to-late 80s qualify as a Tandy original. The Disney games were Apple II originals, the Game Arts games were originally developed for the NEC PC-8801. 3-D Helicopter Simulator does not take advantage of Tandy sound and supports high-res EGA. Thus 11 games from Sierra can be called Tandy 1000 originals with one PCjr. original.
While LucasArts, then Lucasfilm, did not have true Tandy originals, in Maniac Mansion and Zak McKracken their Enhanced versions qualify as Tandy originals. The low-resolution games were developed for the Commodore 64, but the high resolution enhanced versions were clearly developed on the PC. The Amiga and Atari ST versions do not look or sound any better than the PC versions. These games do support EGA graphics. When run in a PCjr., these games will display CGA-quality graphics and PC Speaker sound. The low resolution versions behave identically.
Similarly, the first two games in the SSI Gold Box series, Pool of Radiance and Curse of the Azure Bonds, also had support for the Tandy sound chip and nothing more advanced. However, these were ports from the Commodore 64. On a PCjr., they will need the Tandy mod to show the graphics properly. Hillsfar does not use Tandy Sound and Champions of Krynn, Secret of the Silver Blades and later games support Adlib.
Typically, the main advantage of the PC over every other platform is the prolific availability of hard drives, even (relatively) for the earliest machines, many speeds to choose from and a huge variety of clones to choose from. Who wants to put up with long load times, floppy swaps and inflexible system speeds? The earliest PC games would have been developed for the IBM PC, but most of those games were ports or otherwise historically unimportant and not usually rigidly wedded to IBM's hardware or the CPU speed.
The first historically significant PC game that was released and was not a port was King's Quest. This of course was originally released for the IBM PCjr. The PC version was released soon after and Tandy 1000 version would have been in existence by 1985. The Tandy 1000 version is nearly identical with the PCjr. version. King's Quest II came in one version with support for all three architectures, PC, PCjr. and Tandy 1000. However, it is clear that of these three systems, the best one to play any of Sierra's AGI games is the Tandy 1000. Not only do you get the enhanced graphics and sound, you do not incur the performance penalty of running the first 128K of the PCjr. on the Tandy 1000.
Thus is my definition of a "Tandy Original". First, it must not have been originally developed or released for a non-PC system. No ports from an Apple machine or Atari or Commodore non-IBM PC compatible. Second, the game supports the Tandy Graphics Adapter but no EGA or VGA support, or in the alternative the game supports the Tandy Sound Chip but has no Adlib, Sound Blaster, Roland MT-32 or other sound device support beyond the PC Speaker.
Thus for the AGI-engine games after King's Quest, they were probably developed mostly on Tandy and PC systems. Even King's Quest probably had more work done on it on the PC than on the PCjr. due to the not-insignificant advantages for the PC. When the hard drive installable versions of the games were released, starting with King's Quest III and Space Quest, these were easy to do on the Tandy 1000 and PC compatibles. Since hard drives were an expensive third-party add-on for the PCjr., fewer of these systems enjoyed this feature. I classify all the AGI engine-games as Tandy 1000 originals with two exceptions : King's Quest IV, which was developed for the SCI system and supported much more advanced sound hardware than the Tandy chip and Donald Duck's Playground, which was originally a non-AGI Commodore 64 game.
None of the other games Sierra released during the mid-to-late 80s qualify as a Tandy original. The Disney games were Apple II originals, the Game Arts games were originally developed for the NEC PC-8801. 3-D Helicopter Simulator does not take advantage of Tandy sound and supports high-res EGA. Thus 11 games from Sierra can be called Tandy 1000 originals with one PCjr. original.
While LucasArts, then Lucasfilm, did not have true Tandy originals, in Maniac Mansion and Zak McKracken their Enhanced versions qualify as Tandy originals. The low-resolution games were developed for the Commodore 64, but the high resolution enhanced versions were clearly developed on the PC. The Amiga and Atari ST versions do not look or sound any better than the PC versions. These games do support EGA graphics. When run in a PCjr., these games will display CGA-quality graphics and PC Speaker sound. The low resolution versions behave identically.
Similarly, the first two games in the SSI Gold Box series, Pool of Radiance and Curse of the Azure Bonds, also had support for the Tandy sound chip and nothing more advanced. However, these were ports from the Commodore 64. On a PCjr., they will need the Tandy mod to show the graphics properly. Hillsfar does not use Tandy Sound and Champions of Krynn, Secret of the Silver Blades and later games support Adlib.
Monday, March 25, 2013
IBM PC & PCjr. vs. Tandy 1000 : Price Wars
I recently opined that the Tandy 1000 shared the benefits of the IBM PC and PCjr. while being cheaper than either of them. I wanted to find out how true that was. The IBM PC Model 5150 was released in August, 1981, the PCjr. in January, 1984 and the Tandy 1000 in November, 1984. (I know the Jr. was available for sale in November, 1983, but users actually did not get the machine until January, if they were lucky).
The comparison between the IBM PC and the Tandy 1000 is easy enough. For the prices I am using "A Guide to IBM Personal Computers", January 1985 Edition and the Tandy Radio Shack 1985 Catalog. For the PCjr. prices, I am using the IBM PCjr. Order Form, November 1983 and Compute! Issue 53, October 1984 Article : "IBM's New & Improved PCjr." by Tom R. Halfhill. I know that there could be deals to be had with either system, and you weren't always required to buy the maker's hardware but I am interested in the base price were you to talk into IBM's Business Center or a Radio Shack store.
Lets compare the base system units:
IBM 5150 System Unit Model 176
CPU - Intel 8088 @ 4.77MHz
NPU - Option
RAM - 256K Parity
83-Key Keyboard
5.25" Diskette Drive Adapter
2 x 5.25" Diskette Drives (Full Height)
5 x ISA slots
Base 1985 Price - $2,295.00
Tandy 1000 25-1000
CPU - Intel 8088 @ 4.77MHz
NPU - No Option (until the Tandy 1000A)
RAM - 128K Non-Parity
IBM's 128K Memory Expansion Sidecar would cost $325, but the PCjr. needed a device driver to recognize more than 128K. It was more expensive than the Tandy card and did not add DMA capability, which turned the Tandy 1000 into a truly functional machine.
The comparison between the IBM PC and the Tandy 1000 is easy enough. For the prices I am using "A Guide to IBM Personal Computers", January 1985 Edition and the Tandy Radio Shack 1985 Catalog. For the PCjr. prices, I am using the IBM PCjr. Order Form, November 1983 and Compute! Issue 53, October 1984 Article : "IBM's New & Improved PCjr." by Tom R. Halfhill. I know that there could be deals to be had with either system, and you weren't always required to buy the maker's hardware but I am interested in the base price were you to talk into IBM's Business Center or a Radio Shack store.
Lets compare the base system units:
IBM 5150 System Unit Model 176
CPU - Intel 8088 @ 4.77MHz
NPU - Option
RAM - 256K Parity
83-Key Keyboard
5.25" Diskette Drive Adapter
2 x 5.25" Diskette Drives (Full Height)
5 x ISA slots
Base 1985 Price - $2,295.00
Tandy 1000 25-1000
CPU - Intel 8088 @ 4.77MHz
NPU - No Option (until the Tandy 1000A)
RAM - 128K Non-Parity
90-Key Keyboard
1 x 5.25" Diskette Drive
3 x ISA slots
Also has the following built-in :
Tandy Graphics Adapter (PCjr compatible.)
Tandy Sound (ditto)
Printer Adapter (card-edge)
Game Ports (Tandy joysticks only)
Diskette Drive Adapter (two internal floppies max)
Base 1985 Price - $1,199.00
For almost $1,100 less than what IBM would want, you get virtually all the functionality of the PC and some very nice extras. Parity memory and math co-processor support may have been important to the business world, but was not much of a value for home users. And while 5 ISA slots beats 3 ISA slots, IBM took up two with the floppy controller and any display adapter.
Still, even with this you still need some stuff. Here is the rough equivalent IBM and Tandy upgrade paths and the cost of them :
| IBM Prices Color/Graphics Adapter |
244 |
Tandy Prices Tandy 1000 Disk Drive Kit |
299.95 |
|
| Printer Adapter | 75 | Built-In | ||
| Game Control Adapter | 45 | Built-In | ||
| 5153 Color Display | 680 | CM-2 Color Monitor | 549.95 | |
| PC-DOS 2.1 | 65 | Included | ||
| 256K Memory Expansion Option | 489 | 256K Memory Expansion Board | 299.95 | |
| 128K RAM Upgrade | 149.95 | |||
| 512K Memory Expansion Board | 249.95 | |||
| 5152 Graphics Printer | 449 | DMP-120 | 499.95 |
IBM curiously would be happy to sell you a computer that was unusable for any practical purpose by omitting the display adapter, DOS and in some configurations, floppy drives. I chose IBM's CGA adapter over IBM's recently released Enhanced Graphics Adapter, which while it would provide graphics parity with the Tandy Graphics Adapter, nothing supported it yet. The EGA would set you back an additional $280. Both 14/13" color monitors were suitable for high resolution 640x200 graphics, although the 5153 would have the nicer dot pitch. (.31 vs. .43).
IBM sold either a 64/256K Memory Expansion Option or a 256K Memory Expansion Option. At IBM's prices, a fully stacked 64/256K Memory Expansion Option would cost $565, so I saved money here. However, this adapter uses up slot 3, the Printer Adapter slot 4 and the Game Control Adapter slot 5. No more slots, so there is no room for a second memory expansion or a Asychronous Communications Adapter (Serial) unless you added the 5161 Expansion Unit for the low, low price of $2,585.
Tandy required a memory expansion adapter to upgrade the RAM above 128K. The first ISA adapter came with 128K, supported 128K more and added the very important DMA compatibility. The second ISA adapter also came with 128K but no DMA chip, and 128K more could be added for the maximum 640K. Even though Tandy later released a board that consolidated these two expansions into one, you still had one slot for a serial card or a hard disk controller.
Tandy did not offer a two-floppy system until the SX, but it did include Tandy MS-DOS 2.11 (and GW-BASIC). IBM hit you for extra for DOS. In the 1980s no one could purchase a computer without a printer. The IBM 5152 Graphics Printer was a solid, reliable unit, and I chose the nearest dot-matrix printer from Tandy's Catalog for a comparison. Tandy's printer offerings could get very expensive.
Total IBM PC 1985 Cost : $4,342.00.
Total Tandy 1000 1985 Cost : $3,248.70.
The home user clearly got better value here. IBM had no adapter card that could replicate the PCjr./Tandy Graphics and Sound and no one else did. More and more games were starting to take advantage of them.
But what about the PCjr.? The Enhanced Model was $1,269 at launch but $999 by August 1984. Here is what that would get you :
IBM PCjr. 4863 Model 067
CPU - Intel 8088 @ 4.77MHz
NPU - No Option
RAM - 128K Non-Parity
CPU - Intel 8088 @ 4.77MHz
NPU - No Option
RAM - 128K Non-Parity
62-Key Wireless Infrared Keyboard
1 x 5.25" Diskette Drive
Diskette Drive Adapter
Sidecar Expansion
2 Cartridge Slots
Also has the following built-in :
PCjr. Graphics Adapter
PCjr. Sound
Game Ports
Serial Adapter
Here is what you need to build an roughly equivalent system :
| IBM PCjr. Prices PC-DOS 2.1 |
65 |
Tandy Prices RS-232C Option Board |
99.95 |
|
| Cartridge BASIC | 75 | |||
| Parallel Printer Attachment | 99 |
BASIC was important in the 1980s, and to fully use BASIC on the PCjr., you needed Cartridge BASIC. PC-DOS's BASIC and BASICA required it. Tandy's DOS included GW-BASIC, which incorporated the functions of Cartridge BASIC.
Although I do not know how much IBM charged for the 4863 PCjr. Display, I would assume it was roughly equivalent to the price of the CM-2. If you wanted a cord for the keyboard, that would be an extra $20, payable to IBM. Before the July 31, 1984 price cuts, the IBM and Tandy costs are as follows :
Total IBM PCjr. 1984 Cost : $1,508.00.
Total Tandy 1000 1984 Cost : $1,298.95.
IBM's 128K Memory Expansion Sidecar would cost $325, but the PCjr. needed a device driver to recognize more than 128K. It was more expensive than the Tandy card and did not add DMA capability, which turned the Tandy 1000 into a truly functional machine.
While IBM's price cut and deals would eventually make the system as cheap as the new Tandy 1000 by Christmas 1984, it was scant consolation to those people who bought the PCjr. at full market price, suffered from the chicklet keyboard and found out that someone else bought virtually the exact same system and more expandable to boot only a few months later for more than $200 less. Tandy also had a good Christmas 1984 deal, $999 could get you the 1000 and a Color Monitor (the cheap CM-4). For a realistic user in 1985, the discounts on the PCjr. were not worth it because it was essentially a dead-end system. A well-informed computer buyer, having read magazine articles detailing the troubles with the PCjr. and every conscientious salesperson who did not work for IBM trying to steer customers away from the Peanut should have made scared away potential buyers in droves. All of a sudden, IBM's name no longer held the marquee value it had in the business world, and home computers from Tandy, Commodore and Apple should have looked a lot more attractive.
After March of 1985, when IBM discontinued the PCjr., the system could be had at steep discounts, but there was no future for the machine. Game support quickly disappeared for the PCjr., but for the Tandy 1000 it increased dramatically. Third-party options to add disk and hard drives were very expensive. Tandy could stick it to the customer with prices for its upgrades, and compatibility with PC upgrades could be a little hit-or-miss, but at least there were first and third party options available.
After March of 1985, when IBM discontinued the PCjr., the system could be had at steep discounts, but there was no future for the machine. Game support quickly disappeared for the PCjr., but for the Tandy 1000 it increased dramatically. Third-party options to add disk and hard drives were very expensive. Tandy could stick it to the customer with prices for its upgrades, and compatibility with PC upgrades could be a little hit-or-miss, but at least there were first and third party options available.
Saturday, July 14, 2012
CGA and Tandy Compatibility
Tandy 1000s (except for the RLX and RSXes) have a built-in video adapter which was based on the IBM PCjr.'s internal graphics adapter. However, Tandy decided to do what IBM should have done, which was to make the internal graphics fully CGA compatible. The PCjr. is really only compatible with CGA at the BIOS level, allowing for a 16KB graphics window at B800, implementing a compatible Status Register and using a genuine Motorola 6845 CRTC. It does support CGA color composite video (with a different color palette) and a light pen. Tandy added the Mode and Color Control Registers to allow for full CGA compatibility with software that wrote to those registers directly.
With Tandy's Graphics Adapter, a very high level of compatibility with CGA is maintained. However, it is not perfect for reasons largely not attributable to Tandy. First, IBM and Tandy use slightly different character glyphs in text-mode graphics. IBM's "d" and Tandy's "d" do not look exactly the same, for example. Text characters in text mode or taken from the patterns in the BIOS ROM will look slightly different. This difference would be barely worth mentioning except that games that use tweaked text modes for their graphics will show graphical differences. ICON : Quest for the Ring and The Seven Spirits of RA are the only two examples I can think of. These games use a 40-column text mode where the character cells are 2 pixels high instead of the usual 8. These games are unique in that they use many different text characters instead of solid block characters.
The two screenshots can give you an idea of the differences. First look at this screenshot, using the standard IBM character set :
That is taken from the MACROCOM's ICON demo and that is how it is supposed to look. Now lets look at same screen displayed with the Tandy characters :
I took the above screenshot using MESS, so there are some color errors due to its imperfect CRTC emulation which would not be seen on a real Tandy 1000. But what will be noticeable on the Tandy 1000 is the text, Siegfried's sword arm, the heads of the snakes, the kobold's tail and the Rhine Maid's mouth. The game itself, ICON : Quest for the Rings, is also affected. The 7 Spirits of RA from Sir-Tech uses the same graphics engine and similar anomalies are present in that game.
Second, the composite video colors are also different from IBM's CGA, the PCjr. and Tandy. Although IBM early and late CGA cards have differences in their colors, the differences are minor. Games supporting composite color graphics almost always had their graphics displayed to the IBM CGA standards. Displaying these games on a PCjr. or Tandy 1000 will show the wrong colors outside black, white and maybe the grays. The TV or monitor's tint control may not be sufficient to correct the graphics to the IBM standard. Compare the results here :
http://vogons.zetafleet.com/viewtopic.php?t=12319&postdays=0&postorder=asc&start=500
Third, some games will not display CGA graphics on a Tandy because they detect a Tandy 1000 and will only display Tandy 16-color graphics instead! In that sense, the Tandy is not CGA compatible, again, through no fault of Tandy. Some games offered a command line switch or install program to allow the user to manually specify the graphics mode. 16-color modes generally work better with higher speed processors, so a gamer may have sought to trade graphics quality for game performance on a lower powered machine. Other games do not offer a way to bypass graphics autodetection.
Strangely enough, Tandy SX and TX and later machines with ISA slots will disable the internal Tandy Graphics if a CGA graphics card is installed. Depending on how compatible the CGA card is, #1 should be solvable and #2 may be licked if the character ROM is close enough to IBMs. #3 requires debug talent or replacing the Tandy BIOS ROM with a ROM without the Tandy 1000 identifier byte. (FC00:0000, 21).
With Tandy's Graphics Adapter, a very high level of compatibility with CGA is maintained. However, it is not perfect for reasons largely not attributable to Tandy. First, IBM and Tandy use slightly different character glyphs in text-mode graphics. IBM's "d" and Tandy's "d" do not look exactly the same, for example. Text characters in text mode or taken from the patterns in the BIOS ROM will look slightly different. This difference would be barely worth mentioning except that games that use tweaked text modes for their graphics will show graphical differences. ICON : Quest for the Ring and The Seven Spirits of RA are the only two examples I can think of. These games use a 40-column text mode where the character cells are 2 pixels high instead of the usual 8. These games are unique in that they use many different text characters instead of solid block characters.
The two screenshots can give you an idea of the differences. First look at this screenshot, using the standard IBM character set :
That is taken from the MACROCOM's ICON demo and that is how it is supposed to look. Now lets look at same screen displayed with the Tandy characters :
I took the above screenshot using MESS, so there are some color errors due to its imperfect CRTC emulation which would not be seen on a real Tandy 1000. But what will be noticeable on the Tandy 1000 is the text, Siegfried's sword arm, the heads of the snakes, the kobold's tail and the Rhine Maid's mouth. The game itself, ICON : Quest for the Rings, is also affected. The 7 Spirits of RA from Sir-Tech uses the same graphics engine and similar anomalies are present in that game.
Second, the composite video colors are also different from IBM's CGA, the PCjr. and Tandy. Although IBM early and late CGA cards have differences in their colors, the differences are minor. Games supporting composite color graphics almost always had their graphics displayed to the IBM CGA standards. Displaying these games on a PCjr. or Tandy 1000 will show the wrong colors outside black, white and maybe the grays. The TV or monitor's tint control may not be sufficient to correct the graphics to the IBM standard. Compare the results here :
http://vogons.zetafleet.com/viewtopic.php?t=12319&postdays=0&postorder=asc&start=500
Third, some games will not display CGA graphics on a Tandy because they detect a Tandy 1000 and will only display Tandy 16-color graphics instead! In that sense, the Tandy is not CGA compatible, again, through no fault of Tandy. Some games offered a command line switch or install program to allow the user to manually specify the graphics mode. 16-color modes generally work better with higher speed processors, so a gamer may have sought to trade graphics quality for game performance on a lower powered machine. Other games do not offer a way to bypass graphics autodetection.
Strangely enough, Tandy SX and TX and later machines with ISA slots will disable the internal Tandy Graphics if a CGA graphics card is installed. Depending on how compatible the CGA card is, #1 should be solvable and #2 may be licked if the character ROM is close enough to IBMs. #3 requires debug talent or replacing the Tandy BIOS ROM with a ROM without the Tandy 1000 identifier byte. (FC00:0000, 21).
Thursday, June 21, 2012
IBM PCjr. and Tandy 1000 Games
Originally, I was going to place this article in my Unique PC Hardware and Game Support, but I decided it deserved its separate article. It is well-known that the IBM PCjr. was not a greatly successful home computer. Too expensive, compatibility issues and its upgrade woes doomed it to failure in the marketplace. It was a weird product released by a company that had little prior experience marketing to the consumer market. Even though the machine was only on the market for 18 months, it still had a substantial impact on PC gaming.
That impact was manifested in the Tandy 1000. Released in March, 1985, for the same price as the now discontinued IBM PCjr., $1,199.00, it was a far superior machine and very competitive with an IBM PC 5150. (Actually, Tandy 1000s may have seemed inexpensive, but they got you on their extras). This machine is pretty much what IBM should have released, a true IBM PC compatible with better graphics and sound. Tandy originally intended its computer to be a more compatible PCjr. clone, but when they were ready to release it, the PCjr. discontinuance had been announced and Tandy switched gears and advertised it as an IBM PC compatible.
Unfortunately, in the 18 months of the PCjr.'s life, several games had been released for the IBM PC and PCjr. that would only display advanced graphics and sound if it detected a PCjr. The games determined by the system they were running on by checking the PC identifier byte at F000:FFFE, which was FF for a PC, FD for a PCjr., FE for an early XT and all PC Portables, FB for a later XT, F9 for a PC Convertible and FC for an AT and XT/286. Clones almost invariably identified themselves as PCs to ensure maximum compatibility, and Tandy 1000s were no exception. So those games that detected whether they were being used in a PC or PCjr. would detect a PC if they were being run on a Tandy 1000 and utilize CGA graphics and PC Speaker sound.
There are other compatibility issues between the PCjr. and Tandy 1000s.
Joysticks - The IBM PCjr.'s joysticks work just like IBM PC joysticks. Tandy 1000 joysticks come from the TRS-80 Color Computer and while analog, do not work in exactly the same way as PC joysticks. Usually this is not a big deal, but the differences may cause a game using tight timing loops to get confused.
Floppy Interface - IBM located the floppy adapter at I/O F0-FF on the PCjr., 3F0-3FF on the PC. Tandy went with the PC I/O ports. Games with disk routines (typically for copy protection) that do not use Int 13 and instead directly address the floppy disk controller directly should fail.
BASIC - The IBM PCjr. came with BASIC partially contained in ROM and additionally on a cartridge, the IBM PC came with it partially in ROM, and the Tandy 1000 came with it on solely on a disk. Games that embed or call BASIC or BASICA from IBM PC-DOS in their execution will not work with the Tandy 1000 because those programs require BASIC in ROM.
Keyboard - The IBM PCjr.'s keyboard is basically compatible with the PCs, although not as easy to use due to the fewer keys and the chiclet arrangement. However, with Fn key combinations it is possible to generate all the keystrokes of the PC keyboard. The Tandy 1000's keyboard interface came from the less-than-PC compatible Tandy 2000, and while compatible at the BIOS Int 16 level, there are real differences on how the keyboards work at the hardware level. Games bypassing the BIOS routines may fail to recognize keyboard input.
Cartridges - The Tandy 1000 did not have cartridge ports, so those games that appeared on cartridges only would be beyond the Tandy's capabilities. More ports would have been likely but for the video game crash of 1983.
Memory requires its whole section. First, as the PCjr. was only intended to have 128KB of RAM, the RAM is shared between the CPU and the Video Gate Array. This meant that RAM performance was substantially slower on a PCjr. compared with a PC. Although the original Tandy 1000 also only had 128KB on the motherboard, there are no slowdowns on those machines even though 128KB is shared between video and CPU. Games relying on the slowness of the PCjr. will run too fast on a Tandy 1000.
By the end of 1985, the 128KB of the PCjr. and its abyssmal performance began to be seen as too limiting and developers began to target the Tandy 1000 instead. As the PCjr. was officially dead by March of that year, few developers felt it necessary to support the quirks of the failed system. At this point having a Tandy 1000 was much more important than an IBM PC.
Second, the PCjr. was not designed to be upgradeable beyond 128KB, while the Tandy 1000 was always intended to go up to 640KB. The TX and most of the later models allowed 768KB in the conventional memory space to eliminate the need to take RAM from conventional memory. Eventually IBM thought it would be a good idea to allow memory upgrades to 640KB, but the PCjr. informs programs of its total memory in a different manner compared with PCs and Tandy 1000s. Games requiring 256KB of RAM will not work in a PCjr. unless they are specifically aware of sidecar RAM expansions.
Third, the PCjr. tried to be somewhat compatible with CGA by implementing the CGA graphics window at the B800 segment. It does not have any memory at that area and borrows it from the top of the first 128KB. The PCjr. strictly implemented the window to 16KB. This means that for 32KB graphics modes, 320x200x16 and 640x200x4, only half the graphics would be shown if the programmer wrote to the B800 window. In the PCjr., the graphics would have to be written directly to the 1700 segment. The direct graphics window in the PCjr. would stay within the first 128KB no matter how much expansion sidecar RAM was installed in the system.
Tandy improved on this in two ways. First, it expanded the window at segment B800 to 32KB, allowing all the pixels of the 320x200x16 and 640x200x4 to be shown using that window. Programs did not have to ask the system where the top of the RAM was. Second, the direct graphics memory window is always at the top of RAM up to 640KB. So if a user had maximized his RAM in a pre-TX machine to 640KB, the 512-640KB portion of RAM would be shared between CPU and video. Unfortunately this broke compatibility with PCjr. only-programs that wrote graphics directly to the first 128KB of RAM.
Games automatically detected the Tandy 1000 by first searching the BIOS ROM for the string TANDY. It will be found in any Tandy 1000 because it is shown on the BIOS copyright screen upon bootup. Then it checked the byte at FC00:0000, and if was 21, then the game knew it was running on a Tandy 1000. If not, then the game would assume it was running on another Tandy PC-compatible system like the Tandy 1200 or 3000, which could use regular PC graphic adapters. Games that autodetect a Tandy will utilize the advanced graphics and sound. If a Tandy 1000 was not detected, then the game would use CGA, Hercules or EGA graphics and PC Speaker sound. This occurs even if the game can run in a PCjr.
By 1987, most games did support EGA graphics, which can display identical graphics to the Tandy 1000, so the need for a Tandy 1000 was dwindling. Toward the end of 1988, Sierra and other game companies began supporting discrete sound cards like the Adlib and midi devices like the Roland MT-32. Thus the importance of the 3-voice sound began to wane and by 1990 with the Sound Blaster's digital audio playback support, the need for a Tandy 1000 was all but eliminated.
Rules of thumb for game compatibility :
Game states it supports IBM PC & PCjr. - chances are it will only show 16-color graphics and play 3-voice sound on the PCjr.
Game requires 256KB or greater RAM - chances are it will not work on the IBM PCjr.
Game supports IBM PC, XT, AT, Tandy 1000 - without a specific mention of PCjr. compatibility, assume it will not work on the IBM PCjr., especially if it requires 256KB or more RAM.
Disk-based Game specifically for PCjr. - will probably work more or less in a stock Tandy 1000 or 1000A. Later Tandys come with 256KB or more RAM, and most likely will not work.
Booter games supporting Enhanced Graphics or Sound on PCjr. only :
Agent USA - 320x200x4 resolution, uses solid graphics for better picture on RGB monitors instead of stripey graphics intended for composite color monitors with CGA.#
Alley Cat - 320x200x4, palette uses different colors and not subject to CGA restrictions. Enhanced title screen music,
Bannercatch
Below the Root - Uses 320x200x4, Graphics adjusted for optimal results for composite color display when run on PCjr. Enhanced music on title/demo screen#
Boulder Dash - 160x200x16, 3-voice music and sound effects*
Boulder Dash II - 160x200x16, 3-voice music and sound effects*
Crossfire (Cartridge) - 320x200x4, palette uses different colors and not subject to CGA restrictions.
Jumpman - 160x200x16, 3-voice music and sound effects
Microsoft Flight Simulator 2.0+ - 160x200x16, 3-voice sound effects
Microsurgeon (Cartridge) - 160x200x16, 3-voice music and sound effects
Mine Shaft (Cartridge) - 320x200x4, palette uses different colors and not subject to CGA restrictions.
Mouser (Cartridge) - 160x200x16, 3-voice music and sound effects
Murder on the Zinderneuf - 160x200x16
Oil's Well# - 160x200x16
Pitfall II: Lost Caverns (Cartridge) - 160x200x16, 3-voice music and sound effects
Pitstop 2
River Raid (Cartridge) - 160x200x16, 3-voice music and sound effects
ScubaVenture (Cartridge) - 160x200x16, 3-voice music and sound effects
The Seven Cities of Gold - 640x200x2 composite color (ideal) or 320x200x4 (select by pressing A at title screen), 3-voice music and sound effects
Superbowl Sunday# - 160x200x16
Troll's Tale - 320x200x16 (effective resolution for graphics is 160x200x16)
The World's Greatest Baseball Game - 160x200x16, 3 voice sound effects
* - Super Boulder Dash, which is a compilation booter from Electronic Arts, does support Tandy 1000 graphics and sound, but the available image did not properly crack the Tandy/PCjr. versions of these games, so a fix is required and has been accomplished. The standalone releases of Boulderdash I & II may not support Tandy 1000s because they were released before the Tandy 1000 was released.
# - Tandy 1000 versions of these games may possibly exist, as they were advertised in Radio Shack/Tandy catalogs.
$ - Does not actually support more than four colors on the screen at any time, but can select freely from the 16-color palette, unlike CGA.
% - Modern remake exists with Tandy and VGA support.
@ - Looks best on a composite color monitor or TV.
+ - Supports 256KB (only available with a memory sidecar)
Booter games supporting enhanced graphics or sound on a Tandy 1000 w/256+KB only :
Defender of the Crown - 320x200x16, 3-voice music and sound effects^
Marble Madness - 320x200x4, palette uses different colors and not subject to CGA restrictions, 3-voice music and sound effects.
Sid Meier's Pirates! - 320x200x16, 3-voice music and sound effects^@
Demon's Forge - 320x200x16 - Unknown if 256KB is required
^ - Also supports EGA
$ - Does not actually support more than four colors on the screen at any time, but can select freely from the 16-color palette, unlike CGA.
@ - An official DOS conversion exists that may work with a PCjr. with the Tandy 1000 mod.
Demon Attack (Cartridge for PCjr., Disk for Tandy) - 160x200x16, 3-voice music and sound effects.
King's Quest (PCjr. version probably works on 128KB Tandy, Tandy version works on PCjr.) - 320x200x16 (effective resolution for graphics is 160x200x16)
Touchdown Football - 160x200x16, 3-voice sound effects (including speech!)
The Tandy releases are considerably rarer. Demon Attack for Tandy may have a title screen. The PCjr.'s version of Touchdown Football's speech will be too fast on a Tandy, perhaps the Tandy version fixed that.
DOS games, games which are not self-booting, are usually far more friendly to the Tandy 1000 than the PCjr.
Booter games supporting enhanced graphics or sound on a Tandy 1000 or PCjr. with same program
King's Quest II - Romancing the Throne
The Black Cauldron
Donald Duck's Playground
That impact was manifested in the Tandy 1000. Released in March, 1985, for the same price as the now discontinued IBM PCjr., $1,199.00, it was a far superior machine and very competitive with an IBM PC 5150. (Actually, Tandy 1000s may have seemed inexpensive, but they got you on their extras). This machine is pretty much what IBM should have released, a true IBM PC compatible with better graphics and sound. Tandy originally intended its computer to be a more compatible PCjr. clone, but when they were ready to release it, the PCjr. discontinuance had been announced and Tandy switched gears and advertised it as an IBM PC compatible.
Unfortunately, in the 18 months of the PCjr.'s life, several games had been released for the IBM PC and PCjr. that would only display advanced graphics and sound if it detected a PCjr. The games determined by the system they were running on by checking the PC identifier byte at F000:FFFE, which was FF for a PC, FD for a PCjr., FE for an early XT and all PC Portables, FB for a later XT, F9 for a PC Convertible and FC for an AT and XT/286. Clones almost invariably identified themselves as PCs to ensure maximum compatibility, and Tandy 1000s were no exception. So those games that detected whether they were being used in a PC or PCjr. would detect a PC if they were being run on a Tandy 1000 and utilize CGA graphics and PC Speaker sound.
There are other compatibility issues between the PCjr. and Tandy 1000s.
Joysticks - The IBM PCjr.'s joysticks work just like IBM PC joysticks. Tandy 1000 joysticks come from the TRS-80 Color Computer and while analog, do not work in exactly the same way as PC joysticks. Usually this is not a big deal, but the differences may cause a game using tight timing loops to get confused.
Floppy Interface - IBM located the floppy adapter at I/O F0-FF on the PCjr., 3F0-3FF on the PC. Tandy went with the PC I/O ports. Games with disk routines (typically for copy protection) that do not use Int 13 and instead directly address the floppy disk controller directly should fail.
BASIC - The IBM PCjr. came with BASIC partially contained in ROM and additionally on a cartridge, the IBM PC came with it partially in ROM, and the Tandy 1000 came with it on solely on a disk. Games that embed or call BASIC or BASICA from IBM PC-DOS in their execution will not work with the Tandy 1000 because those programs require BASIC in ROM.
Keyboard - The IBM PCjr.'s keyboard is basically compatible with the PCs, although not as easy to use due to the fewer keys and the chiclet arrangement. However, with Fn key combinations it is possible to generate all the keystrokes of the PC keyboard. The Tandy 1000's keyboard interface came from the less-than-PC compatible Tandy 2000, and while compatible at the BIOS Int 16 level, there are real differences on how the keyboards work at the hardware level. Games bypassing the BIOS routines may fail to recognize keyboard input.
Cartridges - The Tandy 1000 did not have cartridge ports, so those games that appeared on cartridges only would be beyond the Tandy's capabilities. More ports would have been likely but for the video game crash of 1983.
Memory requires its whole section. First, as the PCjr. was only intended to have 128KB of RAM, the RAM is shared between the CPU and the Video Gate Array. This meant that RAM performance was substantially slower on a PCjr. compared with a PC. Although the original Tandy 1000 also only had 128KB on the motherboard, there are no slowdowns on those machines even though 128KB is shared between video and CPU. Games relying on the slowness of the PCjr. will run too fast on a Tandy 1000.
By the end of 1985, the 128KB of the PCjr. and its abyssmal performance began to be seen as too limiting and developers began to target the Tandy 1000 instead. As the PCjr. was officially dead by March of that year, few developers felt it necessary to support the quirks of the failed system. At this point having a Tandy 1000 was much more important than an IBM PC.
Second, the PCjr. was not designed to be upgradeable beyond 128KB, while the Tandy 1000 was always intended to go up to 640KB. The TX and most of the later models allowed 768KB in the conventional memory space to eliminate the need to take RAM from conventional memory. Eventually IBM thought it would be a good idea to allow memory upgrades to 640KB, but the PCjr. informs programs of its total memory in a different manner compared with PCs and Tandy 1000s. Games requiring 256KB of RAM will not work in a PCjr. unless they are specifically aware of sidecar RAM expansions.
Third, the PCjr. tried to be somewhat compatible with CGA by implementing the CGA graphics window at the B800 segment. It does not have any memory at that area and borrows it from the top of the first 128KB. The PCjr. strictly implemented the window to 16KB. This means that for 32KB graphics modes, 320x200x16 and 640x200x4, only half the graphics would be shown if the programmer wrote to the B800 window. In the PCjr., the graphics would have to be written directly to the 1700 segment. The direct graphics window in the PCjr. would stay within the first 128KB no matter how much expansion sidecar RAM was installed in the system.
Tandy improved on this in two ways. First, it expanded the window at segment B800 to 32KB, allowing all the pixels of the 320x200x16 and 640x200x4 to be shown using that window. Programs did not have to ask the system where the top of the RAM was. Second, the direct graphics memory window is always at the top of RAM up to 640KB. So if a user had maximized his RAM in a pre-TX machine to 640KB, the 512-640KB portion of RAM would be shared between CPU and video. Unfortunately this broke compatibility with PCjr. only-programs that wrote graphics directly to the first 128KB of RAM.
Games automatically detected the Tandy 1000 by first searching the BIOS ROM for the string TANDY. It will be found in any Tandy 1000 because it is shown on the BIOS copyright screen upon bootup. Then it checked the byte at FC00:0000, and if was 21, then the game knew it was running on a Tandy 1000. If not, then the game would assume it was running on another Tandy PC-compatible system like the Tandy 1200 or 3000, which could use regular PC graphic adapters. Games that autodetect a Tandy will utilize the advanced graphics and sound. If a Tandy 1000 was not detected, then the game would use CGA, Hercules or EGA graphics and PC Speaker sound. This occurs even if the game can run in a PCjr.
By 1987, most games did support EGA graphics, which can display identical graphics to the Tandy 1000, so the need for a Tandy 1000 was dwindling. Toward the end of 1988, Sierra and other game companies began supporting discrete sound cards like the Adlib and midi devices like the Roland MT-32. Thus the importance of the 3-voice sound began to wane and by 1990 with the Sound Blaster's digital audio playback support, the need for a Tandy 1000 was all but eliminated.
Rules of thumb for game compatibility :
Game states it supports IBM PC & PCjr. - chances are it will only show 16-color graphics and play 3-voice sound on the PCjr.
Game requires 256KB or greater RAM - chances are it will not work on the IBM PCjr.
Game supports IBM PC, XT, AT, Tandy 1000 - without a specific mention of PCjr. compatibility, assume it will not work on the IBM PCjr., especially if it requires 256KB or more RAM.
Disk-based Game specifically for PCjr. - will probably work more or less in a stock Tandy 1000 or 1000A. Later Tandys come with 256KB or more RAM, and most likely will not work.
Booter games supporting Enhanced Graphics or Sound on PCjr. only :
Agent USA - 320x200x4 resolution, uses solid graphics for better picture on RGB monitors instead of stripey graphics intended for composite color monitors with CGA.#
Alley Cat - 320x200x4, palette uses different colors and not subject to CGA restrictions. Enhanced title screen music,
Bannercatch
Below the Root - Uses 320x200x4, Graphics adjusted for optimal results for composite color display when run on PCjr. Enhanced music on title/demo screen#
Boulder Dash - 160x200x16, 3-voice music and sound effects*
Boulder Dash II - 160x200x16, 3-voice music and sound effects*
Crossfire (Cartridge) - 320x200x4, palette uses different colors and not subject to CGA restrictions.
Jumpman - 160x200x16, 3-voice music and sound effects
Microsoft Flight Simulator 2.0+ - 160x200x16, 3-voice sound effects
Microsurgeon (Cartridge) - 160x200x16, 3-voice music and sound effects
Mine Shaft (Cartridge) - 320x200x4, palette uses different colors and not subject to CGA restrictions.
Mouser (Cartridge) - 160x200x16, 3-voice music and sound effects
Murder on the Zinderneuf - 160x200x16
Oil's Well# - 160x200x16
Pitfall II: Lost Caverns (Cartridge) - 160x200x16, 3-voice music and sound effects
Pitstop 2
River Raid (Cartridge) - 160x200x16, 3-voice music and sound effects
ScubaVenture (Cartridge) - 160x200x16, 3-voice music and sound effects
The Seven Cities of Gold - 640x200x2 composite color (ideal) or 320x200x4 (select by pressing A at title screen), 3-voice music and sound effects
Superbowl Sunday# - 160x200x16
Troll's Tale - 320x200x16 (effective resolution for graphics is 160x200x16)
The World's Greatest Baseball Game - 160x200x16, 3 voice sound effects
* - Super Boulder Dash, which is a compilation booter from Electronic Arts, does support Tandy 1000 graphics and sound, but the available image did not properly crack the Tandy/PCjr. versions of these games, so a fix is required and has been accomplished. The standalone releases of Boulderdash I & II may not support Tandy 1000s because they were released before the Tandy 1000 was released.
# - Tandy 1000 versions of these games may possibly exist, as they were advertised in Radio Shack/Tandy catalogs.
$ - Does not actually support more than four colors on the screen at any time, but can select freely from the 16-color palette, unlike CGA.
% - Modern remake exists with Tandy and VGA support.
@ - Looks best on a composite color monitor or TV.
+ - Supports 256KB (only available with a memory sidecar)
Defender of the Crown - 320x200x16, 3-voice music and sound effects^
Marble Madness - 320x200x4, palette uses different colors and not subject to CGA restrictions, 3-voice music and sound effects.
Sid Meier's Pirates! - 320x200x16, 3-voice music and sound effects^@
Demon's Forge - 320x200x16 - Unknown if 256KB is required
^ - Also supports EGA
$ - Does not actually support more than four colors on the screen at any time, but can select freely from the 16-color palette, unlike CGA.
@ - An official DOS conversion exists that may work with a PCjr. with the Tandy 1000 mod.
It is important to note that the following games had separate releases for the PCjr. and Tandy 1000
Demon Attack (Cartridge for PCjr., Disk for Tandy) - 160x200x16, 3-voice music and sound effects.
King's Quest (PCjr. version probably works on 128KB Tandy, Tandy version works on PCjr.) - 320x200x16 (effective resolution for graphics is 160x200x16)
Touchdown Football - 160x200x16, 3-voice sound effects (including speech!)
The Tandy releases are considerably rarer. Demon Attack for Tandy may have a title screen. The PCjr.'s version of Touchdown Football's speech will be too fast on a Tandy, perhaps the Tandy version fixed that.
DOS games, games which are not self-booting, are usually far more friendly to the Tandy 1000 than the PCjr.
Booter games supporting enhanced graphics or sound on a Tandy 1000 or PCjr. with same program
King's Quest II - Romancing the Throne
The Black Cauldron
Donald Duck's Playground
Friday, May 18, 2012
The Other Early Tandy 1000s
Some people may have noticed the prior post in which I extoll the virtues of the Tandy 1000SX. I recently posted on the later Tandy 1000 models, which increasingly stray from the standards established by the PCjr. and original 1000. But let me examine the issues with the other systems.
Tandy 1000TX - This system is equal to or better than the SX in every way but two. It is better in that it has an 80286 CPU, is upgradeable to 768K RAM (to allow full 640K conventional), has a volume control dial for the internal speaker, a front-case mounted headphone jack which reroutes the audio from the internal speaker (no multiplexer nonsense), has a serial port, comes with a 720K drive and boots up a lot faster. However, it provides power through the drive cable, which needs to be accounted for by cutting holes in the pins feeding power to any floppy drive not supporting that arrangement. This is only slightly annoying. Even so, the power supply has one 4-pin Molex connector for the 5.25" floppy drive, which can be split with a common Y-adapter.
The other issue is that the system is by default faster than the SX, even with a 286 Express accelerator. While it can cut the speed of the CPU by half, even a 286 at half speed is substantially faster than an SX without an accelerator.
I would estimate that, based on benchmarks of both systems, Tandy 1000TX running at 4MHz would be somewhat faster than a Tandy 1000SX with a V20 upgrade running at 7.16MHz. However, this is still about 2x faster than an IBM PC with an 8088 running at 4.77MHz. Already you have three noticeable speed increases over the original PC and the software written when that was the only thing around. So if the lower speeds are important to you, then the TX may not be a good choice. Despite running its CPU at 8MHz, the TX and TL machines are approximately 10% slower than an IBM AT @ 8MHz, but have faster video than IBM EGA.
The 286 is in a PLCC socket, so most 386 and 486 upgrade devices work in it, if you can find one. However, it still has 8-bit slots, so you will need to find VGA, IDE, HD Floppy and Network cards that will work in an 8-bit slot.
Tandy 1000EX - This was released at the same time as the SX, and is essentially a stripped down of the SX. It even uses the same BIOS as the SX, shares the 7.16/4.77MHz speed switch. Unfortunately, expansion is really difficult in this machine as it has one bay that is supposed to contain a 5.25" floppy drive. No reset switch either, no way to use a different keyboard, and due to internal RF shielding it is extremely difficult to get inside to the motherboard. I also read that installing a RTC chip is also difficult due to lack of clearance that the internal shielding imposed. No coprocessor can be installed without an extremely rare adapter. The video is difficult to upgrade at best but it is possible despite what Tandy may have told customers.
The worst issue with these machines are the PLUS slots and finding expansion boards. A PLUS slot is simply a 62-pin ISA with berg-strip pins and connectors mounted at a right angle to a regular card edge ISA connector. However, the brackets securing the cards to the chassis are a custom design. Finally, to upgrade the RAM and add DMA you need a special PLUS board similar to the boards for the original 1000s. The most common upgrades to find would be serial cards and modems, and while specialty companies made other upgrade devices, they are extremely difficult to find. There is a port for an external 5.25" or 3.5" drive, but the pinout is a Tandy proprietary design. You can switch the boot drive using the F4 key at bootup. If you have a 3.5" drive, you will need DOS 3.2 and drivparm in your config.sys to obtain the full benefit from it.
The lack of on-board DMA, which users of other computers took for granted, is extremely irritating. Without DMA, most hard drive options are out of reach. Standard MFM/RLL controllers use DMA and memory mapped interface cards like the Trantor T-128 SCSI and the Silicon Valley Computer ADP-50L IDE boards require it to enable their improved performance. You may be able to use a port I/O SCSI interface like the Trantor T-130B, but that will not work reliably unless you have a V20, V30 or 286 CPU.
The other issue is the floppy drive. Without DMA, the CPU must handle all the transfers to and from the floppy drive. This requires tight timing and disabling interrupts, so serial (mouse and modem) and keyboard input may be lost during floppy drive access. DMA makes using old machines much easier.
The machine does have two small benefits over the SX. First, it has an external volume dial that can control the headphone or internal speaker. The SX has a potentiometer inside to adjust the volume, but it isn't very practical to open the case. Second, due to the design you will always get sound output from the jack, unlike the RCA audio output of the 1000 or 1000SX. On the latter machines you may have to set bits in the audio multiplexer. No 8087 coprocessor socket.
Tamdy 1000HX - This update to the EX shares most of its benefits and drawbacks, but adds more in both directions. It was released alongside the TX. Unlike the EX, it has two internal 3.5" bays, although if you want to use them for anything other than Tandy drives you may need some ingenuity in getting other things to fit in them. It can support a third external floppy drive, which can be a 5.25" or a 3.5" drive in addition to the two internal drives.
It has better clearance for installing a clock chip and less RF shielding to contend with. However, it uses power-in-drive cabling for the floppy drives and there are no molex connectors available for powering something else. Although it only comes with DOS 2.11, Tandy modified that DOS to provide full support for 3.5" floppy drives. In theory I suppose that could confuse 3.5" DD floppy programs that say "requires DOS 3.2". It also has DOS-in-ROM, so you don't need a DOS floppy in the drive for simply running applications or have to wait on slow floppy disk accesses to your DOS disk. The machine boots instantly to a menu allowing you to select to boot to a program in drive A:, start from the C: (ROM) drive, or enter Deskmate.
Tandy 1000/A/HD - This is the original model, and it sort of a trial run for the later machines. They have three slots and can expand memory through the use of ISA boards. The original Tandy 1000, (non-A version), has no socket for a numeric 8087 coprocessor. You can burn and insert EPROMs to upgrade to the 01.01.01 BIOS of the 1000A.
The built in graphics cannot be disabled and and using an EGA or VGA card is tricky at best. I do not think that the early 1000s supported the use of a monochrome or Hercules card because there would be no BIOS support for it.
There are only 3 ISA slots, and at least one is required to expand the system beyond 128K and add DMA. Tandy originally released two RAM expansion boards, the first with the DMA chip and up to 256K (25-1004) and the second without.the DMA chip and up to 256K (25-1009). Any RAM card with settable memory addresses like an AST Six Pak Plus (short versions) will work in place of the second card.
For the 1000HD, Tandy included a new board (25-1011) with the DMA chip and allowing you to add up to 512K. It also has a PLUS header allowing you to use a PLUS card, like the serial card, without having to take up another precious slot. The 1000HD also comes with a 10MB MFM hard drive (Tandon TM-252) taking up one of the two 5.25" bays and the interface card (WD1002S-WX2).
Like the SX, the Tandy 1000/A/HD can use the 286 Express Accelerator. The accelerator consists of an ISA card and a daughterboard with a ribbon cable to the motherboard's CPU socket. The Tandy 1000A and 1000HD share the same motherboard, and can use the came daughtercard that the SX can use. The original 1000 requires a different daughteboard, and the regular card is hard enough to find as it is. An NEC V20 will give a modest speed boost.
The Tandy 1000/A/HD system does not assign bootup functions to the F1-F4 keys as the later Tandys do. Since there is only one speed, there is no function for the fast/slow speed, and swap drives is not available (since only one type of drive was supported during these systems' life). Neither is the mono mode, and TV mode (40 columns with 200 lines) requires pressing F12 at bootup. However, the 1000A or the 1000 with upgraded BIOS will allow you to use F1 to enter the mono mode.
There is no volume control and the same issues with the sound multiplexer and the RCA audio out on the SX will be encountered in these machines. Unlike the SX, there is no switch to use IRQ2 instead of IRQ5 for the video (so you can use an IRQ2 hard drive controller). The Power Supply is rated for 54W compared with the 65W of the SX and TX. None of these machines have a Real-Time Clock (RTC), which must be added via a plug-in module. The Dallas DS-1215 is the usual choice.
The 286 is in a PLCC socket, so most 386 and 486 upgrade devices work in it, if you can find one. However, it still has 8-bit slots, so you will need to find VGA, IDE, HD Floppy and Network cards that will work in an 8-bit slot.
Tandy 1000EX - This was released at the same time as the SX, and is essentially a stripped down of the SX. It even uses the same BIOS as the SX, shares the 7.16/4.77MHz speed switch. Unfortunately, expansion is really difficult in this machine as it has one bay that is supposed to contain a 5.25" floppy drive. No reset switch either, no way to use a different keyboard, and due to internal RF shielding it is extremely difficult to get inside to the motherboard. I also read that installing a RTC chip is also difficult due to lack of clearance that the internal shielding imposed. No coprocessor can be installed without an extremely rare adapter. The video is difficult to upgrade at best but it is possible despite what Tandy may have told customers.
The worst issue with these machines are the PLUS slots and finding expansion boards. A PLUS slot is simply a 62-pin ISA with berg-strip pins and connectors mounted at a right angle to a regular card edge ISA connector. However, the brackets securing the cards to the chassis are a custom design. Finally, to upgrade the RAM and add DMA you need a special PLUS board similar to the boards for the original 1000s. The most common upgrades to find would be serial cards and modems, and while specialty companies made other upgrade devices, they are extremely difficult to find. There is a port for an external 5.25" or 3.5" drive, but the pinout is a Tandy proprietary design. You can switch the boot drive using the F4 key at bootup. If you have a 3.5" drive, you will need DOS 3.2 and drivparm in your config.sys to obtain the full benefit from it.
The lack of on-board DMA, which users of other computers took for granted, is extremely irritating. Without DMA, most hard drive options are out of reach. Standard MFM/RLL controllers use DMA and memory mapped interface cards like the Trantor T-128 SCSI and the Silicon Valley Computer ADP-50L IDE boards require it to enable their improved performance. You may be able to use a port I/O SCSI interface like the Trantor T-130B, but that will not work reliably unless you have a V20, V30 or 286 CPU.
The other issue is the floppy drive. Without DMA, the CPU must handle all the transfers to and from the floppy drive. This requires tight timing and disabling interrupts, so serial (mouse and modem) and keyboard input may be lost during floppy drive access. DMA makes using old machines much easier.
The machine does have two small benefits over the SX. First, it has an external volume dial that can control the headphone or internal speaker. The SX has a potentiometer inside to adjust the volume, but it isn't very practical to open the case. Second, due to the design you will always get sound output from the jack, unlike the RCA audio output of the 1000 or 1000SX. On the latter machines you may have to set bits in the audio multiplexer. No 8087 coprocessor socket.
Tamdy 1000HX - This update to the EX shares most of its benefits and drawbacks, but adds more in both directions. It was released alongside the TX. Unlike the EX, it has two internal 3.5" bays, although if you want to use them for anything other than Tandy drives you may need some ingenuity in getting other things to fit in them. It can support a third external floppy drive, which can be a 5.25" or a 3.5" drive in addition to the two internal drives.
It has better clearance for installing a clock chip and less RF shielding to contend with. However, it uses power-in-drive cabling for the floppy drives and there are no molex connectors available for powering something else. Although it only comes with DOS 2.11, Tandy modified that DOS to provide full support for 3.5" floppy drives. In theory I suppose that could confuse 3.5" DD floppy programs that say "requires DOS 3.2". It also has DOS-in-ROM, so you don't need a DOS floppy in the drive for simply running applications or have to wait on slow floppy disk accesses to your DOS disk. The machine boots instantly to a menu allowing you to select to boot to a program in drive A:, start from the C: (ROM) drive, or enter Deskmate.
Tandy 1000/A/HD - This is the original model, and it sort of a trial run for the later machines. They have three slots and can expand memory through the use of ISA boards. The original Tandy 1000, (non-A version), has no socket for a numeric 8087 coprocessor. You can burn and insert EPROMs to upgrade to the 01.01.01 BIOS of the 1000A.
The built in graphics cannot be disabled and and using an EGA or VGA card is tricky at best. I do not think that the early 1000s supported the use of a monochrome or Hercules card because there would be no BIOS support for it.
There are only 3 ISA slots, and at least one is required to expand the system beyond 128K and add DMA. Tandy originally released two RAM expansion boards, the first with the DMA chip and up to 256K (25-1004) and the second without.the DMA chip and up to 256K (25-1009). Any RAM card with settable memory addresses like an AST Six Pak Plus (short versions) will work in place of the second card.
For the 1000HD, Tandy included a new board (25-1011) with the DMA chip and allowing you to add up to 512K. It also has a PLUS header allowing you to use a PLUS card, like the serial card, without having to take up another precious slot. The 1000HD also comes with a 10MB MFM hard drive (Tandon TM-252) taking up one of the two 5.25" bays and the interface card (WD1002S-WX2).
Like the SX, the Tandy 1000/A/HD can use the 286 Express Accelerator. The accelerator consists of an ISA card and a daughterboard with a ribbon cable to the motherboard's CPU socket. The Tandy 1000A and 1000HD share the same motherboard, and can use the came daughtercard that the SX can use. The original 1000 requires a different daughteboard, and the regular card is hard enough to find as it is. An NEC V20 will give a modest speed boost.
The Tandy 1000/A/HD system does not assign bootup functions to the F1-F4 keys as the later Tandys do. Since there is only one speed, there is no function for the fast/slow speed, and swap drives is not available (since only one type of drive was supported during these systems' life). Neither is the mono mode, and TV mode (40 columns with 200 lines) requires pressing F12 at bootup. However, the 1000A or the 1000 with upgraded BIOS will allow you to use F1 to enter the mono mode.
There is no volume control and the same issues with the sound multiplexer and the RCA audio out on the SX will be encountered in these machines. Unlike the SX, there is no switch to use IRQ2 instead of IRQ5 for the video (so you can use an IRQ2 hard drive controller). The Power Supply is rated for 54W compared with the 65W of the SX and TX. None of these machines have a Real-Time Clock (RTC), which must be added via a plug-in module. The Dallas DS-1215 is the usual choice.
Wednesday, May 16, 2012
Benefits and Drawbacks of the Late Model Tandy 1000s
In 1988, Tandy decided to make its very successful 1000 series more like standard PCs and less quirky like its original models. The early model Tandy 1000s were the 1000, A, HD, EX, SX, HX, TX. Late model means Tandy TL, TL/2, TL/3, SL, SL/2, RL, RL-HD, RLX, RLX-HD, RLX-B, RLX-B-HD, RSX, RSX-HD. Now, the later Tandys had some significant advantages over the earlier machines, but they also have their drawbacks too. Lets start with the advantages :
Bays : (TL, TL/2, TL/3)
The first models in the series, the Tandy TL and Tandy SL, were intended to replace the TX and SX in the product line. The TLs have three bays whereas the rest of the Tandys have two. While you do lose some flexibility compared with the two 5.25" bays of the earlier models and SL, you can use one of the 3.5" bays for an internal hard drive.
Drives : (all except SL)
All late model Tandys come with 3.5" drives, which makes using the machines with modern PCs a lot easier. The drives use 720K disks, except for the RLX and RSX, but most 1.44MB USB drives can read and write 720K disks. You can use tape over the hole of HD disks, but best results will be had with true 720K disks.
DOS-in-ROM :
DOS in ROM makes it easier to use the machine without a hard drive. Essentially, the DOS-in-ROM allows you to use DOS formatted disks without needing to have DOS in a floppy drive. Makes for much more convenient and speedier basic disk operations. The DOS in ROM does not include utilities, so you will still need your DOS disks if your programs require DOS utilities. If you have a hard drive, this functionality is disabled.
Fast Booting :
Although the HX and TX started this trend, all late models boot up virtually instantaneously. From the time you turn the power switch on or press reset until the computer begins booting your floppy or hard drive, the time the machine takes is negligible. With DOS-in-ROM, a decent hard drive or compact flash, you will not have to wait for the machine to boot into DOS.
Real Time Clock (TL, TL/2, TL/3, RL-HD, RLX, RLX-B, RLX-B-HD, RSX, RSX-HD) :
The Real Time Clock uses a standard CR2032 Battery in a clip. It is easy to replace. Other systems of this time and later use nasty rechargeable barrel-type batteries or hard to find Dallas 1287 RTCs which have the battery inside the plastic casing. No drivers are required if using Tandy DOS. If you are using a generic DOS, you may need to find a driver, but there is a Tandy MS-DOS 5.00. Nothing higher should be needed for these systems. The SL, SL/2, non-HD RL needs the chip, Dallas DS1216E, installed in a particular socket and has no clip-on battery
EEPROM Saving :
The system settings are stored in a small EEPROM and accessed by a setup program. Earlier systems (HX excluded), had few options to set and those that did would require special parameters (drivparm in config.sys for 720K drives) or jumpers.
Keyboard :
Standard XT keyboards will work and any that can switch to XT mode. IBM Model F XT keyboards work perfectly, and IBM Made (1992 or earlier) Model M keyboards work very well after the first keypress. The Tandy Enhanced Keyboard which came with these systems can work in XT or AT machines, even modern ones. I don't care for the action on the Tandy keyboard, however.
PS/2 Keyboard & Mouse (TL/3, RL, RL-HD, RLX, RLX-HD, RLX-B, RLX-B-HD, RSX, RSX-HD ):
Tandy was particularly forward thinking here, including PS/2 ports for the keyboard and mouse on these systems. No adapters are necessary, and serial mice are slightly more difficult to find than PS/2 mice. Tandys except for the RSX/RSX-HD do not have high IRQs available, and the PS/2 mouse usually uses IRQ 12. The PS/2 mouse of the Tandys uses IRQ3 with the exception noted above, but the cutemouse driver will work fine with the port. Windows will not.
Disable Joystick Ports :
If you do not want to modify a standard PC joystick to work in a Tandy joystick port, which requires building an adapter and internally connecting the third terminal of your joystick axes to ground, you can disable the Tandy joystick ports and use the ports on a standard PC gameport adapter or sound card. Although Tandy did not support doing this, it can be done by setting bit 1 at I/O FFEB to 1.
The RLX-B(-HD) has an 8-pin mini-DIN that requires an adapter to use the regular 6-pin DIN Tandy joysticks.
Card Edge Printer Port Disable (TL,TL/2,SL,SL/2) :
This port is a leftover from the TRS-80s and is designed to be compatible with the pre-IBM Centronics standard. It is not bidirectional and the nybble unidirectional mode doesn't work either. I am unsure whether it can be disabled in the setup program, but it should be disabled by setting bit 1 of I/O 0065 to 0. Other late Tandys come with standard DB-25 ports that are or can be made to work in the bidirectional mode (except the RL and RL-HD).
Built-in Floppy Port Disable (TL,TL/2,SL,SL/2, RL, RL-HD):
You can disable the double density only floppy port through the setup program, allowing for conflict free usage of a high density floppy drive. The TL/3, RLX and RSX come with HD floppy controllers, so even if you could disable them, why would you want to?
Built-in Serial Port Availability and Disable :
All these systems come with a built-in serial port, as does the TX. I am also unsure whether you can disable the 8250B only serial port through the setup program, but it should be doable by setting bit 4 of I/O 0065 to 0. This would allow for the use of a 16450/16550 serial UART controller.
Built-in Graphics Disable (TL, TL/2, TL/3, SL, SL/2, RL, RL-HD) :
The built-in graphics of these Tandys, which are similar to EGA but not compatible with it, can be disabled by plugging in an EGA or VGA card. A program called VGAFIX.COM is required for proper autodetection by some programs. Finding a VGA card that can work in an 8-bit slot will require a bit of work, but the earlier the card, the better. However, even some of the VGA cards using the very fast TSENG ET4000AX cards can work. I am not sure whether the built-in VGA can be disabled the RLX or the SVGA in the RSX, but I doubt anyone would want to sacrifice a slot for that.
CPU Upgradeability (TL, TL/2, TL/3, SL, SL/2) :
The TLs have socketed PLCC 80286s into which plug-in 386 and 486 upgrades can be installed. Unfortunately, due to the lack of extended memory and the difficulty of finding an 8-bit EMS board that will fit in these systems, the functionality is far from a real 386/486. The SLs can have their DIP 8086s replaced with NEC V30s for a speed boost.
Volume Control, Earphone and Microphone Jacks and Reset Switch :
An adjustable knob on the front of the machine allows the user full control over the volume of the internal speaker. Also found on the EX, HX & TX. Reset can be easily accomplished if the system refuses to accept keyboard input, unlike on the EX and HX. Microphone jacks can be used to record sound, and can usually be set to line in as well.
Full 640K Conventional Memory (TL, TL/2, TL/3, RL, RL-HD, RLX, RLX-B, RLX-B-HD, RSX, RSX-HD) :
Unlike all the earlier Tandys except the TX, most of the later models have a 128K upgrade so that the full 640K is available instead of 32K or more taken by the built-in graphics. (RLX & RSX do not apply as they have VGA, which does not rob from system RAM)
Expanded/Extended Memory (RLX, RLX-B, RLX-B-HD, RSX, RSX-HD) :
The RLX/RLX-B can be upgraded to 1MB of RAM, and the HD versions have the 1MB preinstalled. 640K is conventional, 384K is extended. I assume the the 384K of extended is mapped above 1MB, so it can only be used for whatever you can use extended memory. You can use it to load DOS high and save about 40K using HIMEM.SYS /M:2. You can also use it for games that support the XMS standard, SMARTDRV disk cache and programs that use the 286's protected mode like Windows 3.0 & 3.1. Unfortunately, more games used EMS than XMS because EMS works in 808x machines, but EMS is not possible on this machine unless you use its slot for an EMS board. The RSX can be upgraded to 9MB, and that can be easily configured to act as expanded or extended memory thanks to the 386's memory controller and EMM386.EXE and HIMEM.SYS.
Compact and Silent Running (RL, RL-HD, RLX, RLX-B, RLX-B-HD, RSX, RSX-HD)
These machines are very small, both in terms of case height/width/depth and the motherboard size. Additionally, their power supplies are only 25W, so they do not use a fan. This means that unless you are accessing a drive motor or using the speaker, these machines run silently. The drawback is the limited expansion, one or two ISA slots only. The bidirectional parallel port can help out here.
Drawbacks :
Video :
No composite video
None of the later Tandys support composite video output, while all the early ones do. Although there are detection issues, you can put a CGA card in these Tandys for composite video output. Unlike the early Tandys and PCjr., you will be limited to the CGA modes for composite color.
Hercules graphics (TL, TL/2, TL/3, SL, SL/2, RL, RL-HD)
Games autodetecting Tandy may not work with the Hercules emulation found in the Tandy Video II chip. They detect a Tandy 1000 and assume that the user wants to use Tandy graphics, regardless of any other functionality detected. Of course, since most games look better with color graphics, the Hercules/MDA functionality is likely to go unused. Dual monitor support, using a splitter cable, is theoretically possible, however, this may endanger your monitors, which function at different sync rates. A CGA and a MDA monitor may be damaged if the other's monitor's scan rates are sent to it.
Audio :
Slight audio issues :
There maybe some missing notes in Tandy music. The first note of Greensleeves on KQ1 (DOS) and KQ2 (booter or DOS) will not play on any later Tandy. This is because the Sierra AGI engine will send a command to set the audio multiplexer to output to the RCA jacks on the Tandy 1000 and SX. This functionality is not required for any other Tandy, and the write will reset the PSSJ chip in the later models, causing the first note not to be played. The early Tandys and PCjr. have a discrete sound chip, the TI SN 76496, but the later Tandys have that functionality built into its PSSJ chip.
The digital audio recording for the TL and SL is speed dependent. The TL/2 and SL/2 and later Tandy's have a double buffered input, so recording audio is no longer speed dependent.
Conflicts with devices using DMA1
The later Tandys will freeze if a Sound Blaster 1.0-2.0, which cannot use anything else but DMA1, is installed in the system if digitized sound is played back. You may encounter this in a game supporting either Sound Blaster or the Tandy DAC. There may also be problems, for example, with a Central Point Software CopyIIPC Option Board, which must use DMA1 in a Tandy 1000 (can share DMA2 in an IBM PC).
No Tandy sound (RLX, RLX-HD, RLX-B, RLX-B-HD, RSX, RSX-HD)
The RLX and RSX really strayed far from the Tandy 1000 standard. The RLX does not support Tandy graphics because it has a standard VGA built into the motherboard. So games that autodetect the graphics and sound may not play the Tandy sounds if they find a non-Tandy graphics adapter in the system. The RSX went even further from the compatibility ideal, as it had moved the sound chip from I/O C0 to 1E0 because it supported the 2nd DMA controller, which can be found at C0. Most programs supporting Tandy sound were released prior to the RSX and were unaware of the move. Moreover, there were no BIOS routines for the music, the programmer had to write to the sound chip directly. There were BIOS routines for digitized sound playback, so if the game used them, that sound would work. Not all games did. The Tandy 2500XL also had the sound chip relocated, so you can use that selection if your game supports it.
No joystick during digital audio playback
The PSSJ chip will not allow joystick reads while it is playing back digitized sounds. This may only be slightly annoying, as most games of the time period only use short snippets. However, if the game uses frequent digital samples, then it may disable the joystick entirely. I doubt it would read from an IBM gameport, since it does not expect one to be in a Tandy 1000.
Peripherals
Keyboard :
Programs demanding the original Tandy 1000 keyboard may have serious difficulties. First, the scan codes for the F11, F12 and dedicated cursor keys on the original Tandy 1000 keyboard cannot be generated by the corresponding key of a standard 101-key keyboard, whether in XT or AT mode. This is usually not too much of a problem as most programs in the 1980s did not use F11 & F12 and would allow you to use the numeric keypad as cursor keys. Any games that rely on differences in the Tandy keyboard may be tricky or impossible to play on an IBM PC keyboard. Finally, some games may refuse to accept input (Snow Strike) or freeze (King's Quest Tandy Booter) on some keys because they expect the Tandy keyboard and get an IBM keyboard instead.
On the SL and TL, it may be possible to make an adapter to allow the original 1000 keyboard to work.
Joystick :
Programs requiring the Tandy joystick port used may not read the stick correctly if the Tandy ports are disabled and an IBM PC joystick is being used instead. There are differences in how the ports work at the electrical level. Really early games would not know of the Tandy joystick and their tight timing loops may be thrown off by the differences. Later games may take those differences into account in their reading routines and not work properly because the hardware does not exactly match what they are expecting. I do not know of a game that definitively has this issue, so this may be more of a theoretical than a real compatibility issue.
Interfaces :
Power-in-Drive Cables (TL, TL/2, TL/3, SL/2, RL, RL-HD, RLX, RLX-HD, RLX-B, RLX-B-HD, RSX, RSX-HD) :
In a normal IBM PC, power is supplied to drives on a separate cable with a 4-pin Molex or mini-Molex plug from the 34-pin data ribbon cable. In all Tandys from the TX and HX onward, except for the SL, +5 and +12 v is supplied on what would otherwise be ground pins on a normal drive cable. Some Tandy cables, which tend to be no longer than absolutely necessary for Tandy supplied drives, had holes punched in the cables for a 5.25" drive.
8-bit IDE interface (TL/2, TL/3, RL, RL-HD, RLX, RLX-HD, RLX-B, RLX-B-HD) :
This may have been a good idea at the time, but today is fairly useless. In the early days of the IDE standard, there was an 8-bit version released for 8-bit machines. As Tandy never implemented 16-bit slots or 16-bit IDE ports until the RSX on the 1000 series, they sold 8-bit IDE drives. Unfortunately these drives are very difficult to find today and only come in 20 and 40MB varieties. Regular 16-bit IDE hard drives and compact flash drives will not work with these ports. Compared to the TL, the TL/2 and TL/3 sacrifice a slot for this interface.
8-bit slots (TL, TL/2, TL/3, SL, SL/2, RL, RL-HD, RLX, RLX-HD, RLX-B, RLX-B-HD) :
Unfortunately, even though half systems have a 80286 and therefore naturally support 16-bit data bus transfers, Tandy crippled their machines. Only the RSX has 16-bit slots, and it is the least compatible of the lot. All the above machines could have supported a full or crippled ISA slot. The 8086 supports a 16-bit data bus and the upper address lines on a 16-bit slot are not used on all cards. The same could be said for the TX as well.
Bays : (TL, TL/2, TL/3)
The first models in the series, the Tandy TL and Tandy SL, were intended to replace the TX and SX in the product line. The TLs have three bays whereas the rest of the Tandys have two. While you do lose some flexibility compared with the two 5.25" bays of the earlier models and SL, you can use one of the 3.5" bays for an internal hard drive.
Drives : (all except SL)
All late model Tandys come with 3.5" drives, which makes using the machines with modern PCs a lot easier. The drives use 720K disks, except for the RLX and RSX, but most 1.44MB USB drives can read and write 720K disks. You can use tape over the hole of HD disks, but best results will be had with true 720K disks.
DOS-in-ROM :
DOS in ROM makes it easier to use the machine without a hard drive. Essentially, the DOS-in-ROM allows you to use DOS formatted disks without needing to have DOS in a floppy drive. Makes for much more convenient and speedier basic disk operations. The DOS in ROM does not include utilities, so you will still need your DOS disks if your programs require DOS utilities. If you have a hard drive, this functionality is disabled.
Fast Booting :
Although the HX and TX started this trend, all late models boot up virtually instantaneously. From the time you turn the power switch on or press reset until the computer begins booting your floppy or hard drive, the time the machine takes is negligible. With DOS-in-ROM, a decent hard drive or compact flash, you will not have to wait for the machine to boot into DOS.
Real Time Clock (TL, TL/2, TL/3, RL-HD, RLX, RLX-B, RLX-B-HD, RSX, RSX-HD) :
The Real Time Clock uses a standard CR2032 Battery in a clip. It is easy to replace. Other systems of this time and later use nasty rechargeable barrel-type batteries or hard to find Dallas 1287 RTCs which have the battery inside the plastic casing. No drivers are required if using Tandy DOS. If you are using a generic DOS, you may need to find a driver, but there is a Tandy MS-DOS 5.00. Nothing higher should be needed for these systems. The SL, SL/2, non-HD RL needs the chip, Dallas DS1216E, installed in a particular socket and has no clip-on battery
EEPROM Saving :
The system settings are stored in a small EEPROM and accessed by a setup program. Earlier systems (HX excluded), had few options to set and those that did would require special parameters (drivparm in config.sys for 720K drives) or jumpers.
Keyboard :
Standard XT keyboards will work and any that can switch to XT mode. IBM Model F XT keyboards work perfectly, and IBM Made (1992 or earlier) Model M keyboards work very well after the first keypress. The Tandy Enhanced Keyboard which came with these systems can work in XT or AT machines, even modern ones. I don't care for the action on the Tandy keyboard, however.
PS/2 Keyboard & Mouse (TL/3, RL, RL-HD, RLX, RLX-HD, RLX-B, RLX-B-HD, RSX, RSX-HD ):
Tandy was particularly forward thinking here, including PS/2 ports for the keyboard and mouse on these systems. No adapters are necessary, and serial mice are slightly more difficult to find than PS/2 mice. Tandys except for the RSX/RSX-HD do not have high IRQs available, and the PS/2 mouse usually uses IRQ 12. The PS/2 mouse of the Tandys uses IRQ3 with the exception noted above, but the cutemouse driver will work fine with the port. Windows will not.
Disable Joystick Ports :
If you do not want to modify a standard PC joystick to work in a Tandy joystick port, which requires building an adapter and internally connecting the third terminal of your joystick axes to ground, you can disable the Tandy joystick ports and use the ports on a standard PC gameport adapter or sound card. Although Tandy did not support doing this, it can be done by setting bit 1 at I/O FFEB to 1.
The RLX-B(-HD) has an 8-pin mini-DIN that requires an adapter to use the regular 6-pin DIN Tandy joysticks.
Card Edge Printer Port Disable (TL,TL/2,SL,SL/2) :
This port is a leftover from the TRS-80s and is designed to be compatible with the pre-IBM Centronics standard. It is not bidirectional and the nybble unidirectional mode doesn't work either. I am unsure whether it can be disabled in the setup program, but it should be disabled by setting bit 1 of I/O 0065 to 0. Other late Tandys come with standard DB-25 ports that are or can be made to work in the bidirectional mode (except the RL and RL-HD).
Built-in Floppy Port Disable (TL,TL/2,SL,SL/2, RL, RL-HD):
You can disable the double density only floppy port through the setup program, allowing for conflict free usage of a high density floppy drive. The TL/3, RLX and RSX come with HD floppy controllers, so even if you could disable them, why would you want to?
Built-in Serial Port Availability and Disable :
All these systems come with a built-in serial port, as does the TX. I am also unsure whether you can disable the 8250B only serial port through the setup program, but it should be doable by setting bit 4 of I/O 0065 to 0. This would allow for the use of a 16450/16550 serial UART controller.
Built-in Graphics Disable (TL, TL/2, TL/3, SL, SL/2, RL, RL-HD) :
The built-in graphics of these Tandys, which are similar to EGA but not compatible with it, can be disabled by plugging in an EGA or VGA card. A program called VGAFIX.COM is required for proper autodetection by some programs. Finding a VGA card that can work in an 8-bit slot will require a bit of work, but the earlier the card, the better. However, even some of the VGA cards using the very fast TSENG ET4000AX cards can work. I am not sure whether the built-in VGA can be disabled the RLX or the SVGA in the RSX, but I doubt anyone would want to sacrifice a slot for that.
CPU Upgradeability (TL, TL/2, TL/3, SL, SL/2) :
The TLs have socketed PLCC 80286s into which plug-in 386 and 486 upgrades can be installed. Unfortunately, due to the lack of extended memory and the difficulty of finding an 8-bit EMS board that will fit in these systems, the functionality is far from a real 386/486. The SLs can have their DIP 8086s replaced with NEC V30s for a speed boost.
Volume Control, Earphone and Microphone Jacks and Reset Switch :
An adjustable knob on the front of the machine allows the user full control over the volume of the internal speaker. Also found on the EX, HX & TX. Reset can be easily accomplished if the system refuses to accept keyboard input, unlike on the EX and HX. Microphone jacks can be used to record sound, and can usually be set to line in as well.
Full 640K Conventional Memory (TL, TL/2, TL/3, RL, RL-HD, RLX, RLX-B, RLX-B-HD, RSX, RSX-HD) :
Unlike all the earlier Tandys except the TX, most of the later models have a 128K upgrade so that the full 640K is available instead of 32K or more taken by the built-in graphics. (RLX & RSX do not apply as they have VGA, which does not rob from system RAM)
Expanded/Extended Memory (RLX, RLX-B, RLX-B-HD, RSX, RSX-HD) :
The RLX/RLX-B can be upgraded to 1MB of RAM, and the HD versions have the 1MB preinstalled. 640K is conventional, 384K is extended. I assume the the 384K of extended is mapped above 1MB, so it can only be used for whatever you can use extended memory. You can use it to load DOS high and save about 40K using HIMEM.SYS /M:2. You can also use it for games that support the XMS standard, SMARTDRV disk cache and programs that use the 286's protected mode like Windows 3.0 & 3.1. Unfortunately, more games used EMS than XMS because EMS works in 808x machines, but EMS is not possible on this machine unless you use its slot for an EMS board. The RSX can be upgraded to 9MB, and that can be easily configured to act as expanded or extended memory thanks to the 386's memory controller and EMM386.EXE and HIMEM.SYS.
Compact and Silent Running (RL, RL-HD, RLX, RLX-B, RLX-B-HD, RSX, RSX-HD)
These machines are very small, both in terms of case height/width/depth and the motherboard size. Additionally, their power supplies are only 25W, so they do not use a fan. This means that unless you are accessing a drive motor or using the speaker, these machines run silently. The drawback is the limited expansion, one or two ISA slots only. The bidirectional parallel port can help out here.
Drawbacks :
Video :
No composite video
None of the later Tandys support composite video output, while all the early ones do. Although there are detection issues, you can put a CGA card in these Tandys for composite video output. Unlike the early Tandys and PCjr., you will be limited to the CGA modes for composite color.
Hercules graphics (TL, TL/2, TL/3, SL, SL/2, RL, RL-HD)
Games autodetecting Tandy may not work with the Hercules emulation found in the Tandy Video II chip. They detect a Tandy 1000 and assume that the user wants to use Tandy graphics, regardless of any other functionality detected. Of course, since most games look better with color graphics, the Hercules/MDA functionality is likely to go unused. Dual monitor support, using a splitter cable, is theoretically possible, however, this may endanger your monitors, which function at different sync rates. A CGA and a MDA monitor may be damaged if the other's monitor's scan rates are sent to it.
Audio :
Slight audio issues :
There maybe some missing notes in Tandy music. The first note of Greensleeves on KQ1 (DOS) and KQ2 (booter or DOS) will not play on any later Tandy. This is because the Sierra AGI engine will send a command to set the audio multiplexer to output to the RCA jacks on the Tandy 1000 and SX. This functionality is not required for any other Tandy, and the write will reset the PSSJ chip in the later models, causing the first note not to be played. The early Tandys and PCjr. have a discrete sound chip, the TI SN 76496, but the later Tandys have that functionality built into its PSSJ chip.
The digital audio recording for the TL and SL is speed dependent. The TL/2 and SL/2 and later Tandy's have a double buffered input, so recording audio is no longer speed dependent.
Conflicts with devices using DMA1
The later Tandys will freeze if a Sound Blaster 1.0-2.0, which cannot use anything else but DMA1, is installed in the system if digitized sound is played back. You may encounter this in a game supporting either Sound Blaster or the Tandy DAC. There may also be problems, for example, with a Central Point Software CopyIIPC Option Board, which must use DMA1 in a Tandy 1000 (can share DMA2 in an IBM PC).
No Tandy sound (RLX, RLX-HD, RLX-B, RLX-B-HD, RSX, RSX-HD)
The RLX and RSX really strayed far from the Tandy 1000 standard. The RLX does not support Tandy graphics because it has a standard VGA built into the motherboard. So games that autodetect the graphics and sound may not play the Tandy sounds if they find a non-Tandy graphics adapter in the system. The RSX went even further from the compatibility ideal, as it had moved the sound chip from I/O C0 to 1E0 because it supported the 2nd DMA controller, which can be found at C0. Most programs supporting Tandy sound were released prior to the RSX and were unaware of the move. Moreover, there were no BIOS routines for the music, the programmer had to write to the sound chip directly. There were BIOS routines for digitized sound playback, so if the game used them, that sound would work. Not all games did. The Tandy 2500XL also had the sound chip relocated, so you can use that selection if your game supports it.
No joystick during digital audio playback
The PSSJ chip will not allow joystick reads while it is playing back digitized sounds. This may only be slightly annoying, as most games of the time period only use short snippets. However, if the game uses frequent digital samples, then it may disable the joystick entirely. I doubt it would read from an IBM gameport, since it does not expect one to be in a Tandy 1000.
Peripherals
Keyboard :
Programs demanding the original Tandy 1000 keyboard may have serious difficulties. First, the scan codes for the F11, F12 and dedicated cursor keys on the original Tandy 1000 keyboard cannot be generated by the corresponding key of a standard 101-key keyboard, whether in XT or AT mode. This is usually not too much of a problem as most programs in the 1980s did not use F11 & F12 and would allow you to use the numeric keypad as cursor keys. Any games that rely on differences in the Tandy keyboard may be tricky or impossible to play on an IBM PC keyboard. Finally, some games may refuse to accept input (Snow Strike) or freeze (King's Quest Tandy Booter) on some keys because they expect the Tandy keyboard and get an IBM keyboard instead.
On the SL and TL, it may be possible to make an adapter to allow the original 1000 keyboard to work.
Joystick :
Programs requiring the Tandy joystick port used may not read the stick correctly if the Tandy ports are disabled and an IBM PC joystick is being used instead. There are differences in how the ports work at the electrical level. Really early games would not know of the Tandy joystick and their tight timing loops may be thrown off by the differences. Later games may take those differences into account in their reading routines and not work properly because the hardware does not exactly match what they are expecting. I do not know of a game that definitively has this issue, so this may be more of a theoretical than a real compatibility issue.
Interfaces :
Power-in-Drive Cables (TL, TL/2, TL/3, SL/2, RL, RL-HD, RLX, RLX-HD, RLX-B, RLX-B-HD, RSX, RSX-HD) :
In a normal IBM PC, power is supplied to drives on a separate cable with a 4-pin Molex or mini-Molex plug from the 34-pin data ribbon cable. In all Tandys from the TX and HX onward, except for the SL, +5 and +12 v is supplied on what would otherwise be ground pins on a normal drive cable. Some Tandy cables, which tend to be no longer than absolutely necessary for Tandy supplied drives, had holes punched in the cables for a 5.25" drive.
8-bit IDE interface (TL/2, TL/3, RL, RL-HD, RLX, RLX-HD, RLX-B, RLX-B-HD) :
This may have been a good idea at the time, but today is fairly useless. In the early days of the IDE standard, there was an 8-bit version released for 8-bit machines. As Tandy never implemented 16-bit slots or 16-bit IDE ports until the RSX on the 1000 series, they sold 8-bit IDE drives. Unfortunately these drives are very difficult to find today and only come in 20 and 40MB varieties. Regular 16-bit IDE hard drives and compact flash drives will not work with these ports. Compared to the TL, the TL/2 and TL/3 sacrifice a slot for this interface.
8-bit slots (TL, TL/2, TL/3, SL, SL/2, RL, RL-HD, RLX, RLX-HD, RLX-B, RLX-B-HD) :
Unfortunately, even though half systems have a 80286 and therefore naturally support 16-bit data bus transfers, Tandy crippled their machines. Only the RSX has 16-bit slots, and it is the least compatible of the lot. All the above machines could have supported a full or crippled ISA slot. The 8086 supports a 16-bit data bus and the upper address lines on a 16-bit slot are not used on all cards. The same could be said for the TX as well.
Sunday, August 7, 2011
Tandy 1000SX - The Best Overall Choice for IBM PC Gaming of the 1980s
Back in the 1980s, if you wanted to play games on a computer, there were many incompatible options available. If you were on a budget, you may have had a Commodore 64. If you were a real computer geek, you may have appreciated the open system of the Apple II. Of course, your parents may have made the unfortunate choice of buying a Coleco Adam, Mattel Aquarius, TI-994A, a Commodore PET or TSR-80 or Color Computer. None of these machines were particularly good for gaming. You may have had the awesome parents that would have bought an Atari 8-bit computer or the VIC-20, which were great for games and very little else. But later in the 1980s there were fewer options, in no small part due to the acceptance of the IBM PC in the business world.
In the second half of the 1980s, the 6502-based systems like the C64 and Apple II were really starting to show their age and the Atari machine was virtually dead. In response, Commodore, Atari and Apple introduced new computers, the Amiga, ST, Macintosh and IIgs respectively. The first two never caught on in the North American market, the Macintosh suffered from a lack of a color screen and gaming hardware early in its life and the IIgs withered on the vine due to a perceived slow processor and apathy from Apple.
From 1981-1986, the IBM PC line had become a huge success in the business world, but the high prices of the offerings from IBM did not make for much enthusiasm from the home market. Even in 1987, just before IBM discontinued the line, the most basic configuration of the IBM PC cost a list price of $1,165.00. This configuration only came with 64KB of RAM, no floppy or hard disk drive or adapter, no monitor or graphics card, no software, no game controller adapter. To get a working configuration you would practically have to double the price. For that year, the PC was a slow machine.
IBM's one effort to market a machine to the home user during this decade was the PCjr from 1983-1985. The Jr. failed for reasons that are widely known, namely that people were expecting a fully PC compatible machine and got something significantly less than compatible, had a terrible chicklet keyboard, limited and proprietary expansion options, and was not especially competitive with other home computers at the high price point of $1,269.00. If the PCjr. could not escape the shadow of its big brother and its own shortcomings, it did have some influence. First, it was designed to be easier to get up and running. If you got the expanded model, there was little need to open the machine as everything attached to the back or was bolted onto the side. It had lots of built in hardware that were extras on a PC. It had a built-in custom graphics controller that had better capabilities than the Color/Graphics Monitor Adapter found on the PC and could connect to a digital RGB or analog composite color monitor. Comparable but incompatible graphics were available on the Enhanced Graphics Adapter, which was hugely expensive at the time. It had a three-voice sound chip in addition to the PC Speaker and could mix external audio from a sidecar and had an audio RCA output. All the above did not exist on the PC. It had a serial port and a game port with plugs for two joysticks, which were extra add-in cards on the PC. Perhaps in part to offset speed issues with RAM shared between the CPU and the Graphics Controller, the machine had two cartridge slots for games and programs.
Tandy Corporation, which operated the Radio Shack chain of stores, had a very active home computer division which had already produced the aging TRS-80 and not-exactly a sales leader Color Computer lines. Tandy had designed an MS-DOS machine called the Tandy 2000, which was at best semi-compatible with the PC and was hardly a best-seller. The home market was crying out for affordable PC-compatible machines, and Tandy liked the PCjr.'s features and thought they could do better at the price point. They developed a machine that supported the PCjr.s features and offered mostly better PC-compatibility. Unfortunately, in 1985 as the machine was about to be released, IBM discontinued the Jr. So Tandy began to emphasize MS-DOS and PC compatiblility for the machine, the Tandy 1000.
The Tandy 1000 came with a 8088 running at 4.77MHz, just like a PC, 128KB of RAM (shared with graphics), the 90-key Keyboard used in the Tandy 2000, two joystick ports using joysticks from the CoCo, the same graphics and sound capabilities as the PCjr., composite video and digital RGB support, a printer port. Its keyboard and joystick ports were at the front of the unit whereas IBM's were always at the back. It had a reset button whereas IBM users had to press Ctrl-Alt-Del. It ditched the cassette and cartridge ports of the Jr., the wireless keyboard and avoided proprietary ports to a greater extent than the Jr. It came with a 5.25" floppy disk as standard and had the floppy controller circuitry built into the motherboard. MS-DOS 2.11 and GW-BASIC came with the machine (no separate purchase required) as did DeskMate (Office App). Unlike the PCjr. with its one drive bay, the 1000 came with two. Its weaknesses included :
Only 3 XT/8-bit ISA slots
RAM upgrades only by special Tandy upgrade cards took up 1-2 ISA slots to get to 640KB.
No Serial port
No DMA built-in, came on one of the RAM upgrades. This gave a stock 1000 the same kind of annoyances as the Jr. (CPU servicing disk drive, leading to ignored keystrokes, keystrokes interrupting serial data).
No ability to disable graphics circuitry (no upgrades to EGA or VGA)
No socket for a Math Coprocessor.
The Tandy 1000A added a math coprocessor socket and fixed some bugs. (Tandy offered a version called the 1000HD with a 10MB hard drive and a 640KB RAM & DMA upgrade board that came on 1 board instead of 2). The IRQ for the hard drive was 2 for these Tandys, with IRQ 5 used for the video. IBM used the opposite designations for the PC line.
The next models in the series, released toward the end of 1986, are the Tandy 1000 EX and 1000 SX. They are functionally the same machine, but the EX is a compact model with only one drive bay and the need to use Plus card for expansion with room for only three and an external drive port for a second disk drive. The RAM and DMA upgrade comes on a Plus card.
The Tandy 1000 SX, the machine in question fixes virtually all the above issues. It has 5 XT/8-bit ISA slots, can be upgraded to 640KB of RAM on the motherboard, can support an EGA or VGA card and a hard disk controller and a math coprocessor. It came with 384KB standard RAM, a DMA chip and used standard 256Kx1 chips to upgrade to 640KB. It came with MS-DOS 3.2, which added support for 720KB drives. It could boot from either drive, which is useful if you have bootable 5.25" and 3.5" disks. It ran is 8088 at 7.16MHz or 4.77MHz for a decent speed boost. This speed is selectable on bootup for software expecting the slower speed.
Later models in the 1000 series added support for a 286 processor (TX), DOS-in-ROM (HX), 768KB of RAM so graphics memory would not conflict with conventional memory (TX), high density floppy controller (RLX & TL/3), 8-bit IDE interface (TL/2, RL), 3.5" drives as standard (TX & HX), improved graphics with 640x200x16 mode (TL & SL), enhanced sound with Digital-to-Analog and Analog-to-Digital conversion (Tl & SL).
Here is how I have my Tandy 1000 SX configured
Monitor :
Tandy CM-11 High Resolution Color Monitor
Keyboard :
Tandy 1000 Keyboard
Drive Bays :
5.25" 360KB Drive
3.5" 720KB Drive
ISA Slots :
1 - Serial Card
2 - 286xpres Accelerator
3 - Roland MIF-IPC-A w/ Roland MPU-401 & Roland MT-32
4 - Adlib Music Synthesizer Card or Creative Game Blaster Card
5 - ADP-50L 16-bit IDE Controller
I feel no particular need to go 100% Tandy, but the floppy drives come from, if not manufactured by, Tandy. I used to have a 20MB Tandy Hardcard, but the drive was very noisy and soon died. So, in my only concession to modern hardware, I have a 1.0GB Compact Flash card mounted instead. Unfortunately, the ADP card, which supports 16-bit IDE drives on an 8-bit bus, can only utilize 504MB of that due to the infamous limitations of the straight INT 13h/ATA addressing it uses. This limitation is independent of any DOS limitations. Compact Flash cards are virtually IDE devices, requiring only a passive pin converter to work with an IDE port. The ADP card is a bit finicky about which CF drives it will boot, having not been designed for that. The Board does not use IRQs or DMAs. Two drives can be used for a total of 1008MB. The ADP board relies on memory mapped I/O, not port mapped I/O, so it should be faster than, say an XT-IDE card. (The XT-IDE card with a 2.0 and above BIOS eliminates virtually all hard drive barriers, but even MS-DOS 6.22 and Windows 95 pre-OSR2 only support physical disks up to 8GB). I may also be able to use a Trantor T-130B 8-bit SCSI interface card but that requires a separate SCSI-IDE bridge. On the plus side, it does support and can boot up to 1GB storage devices. However, the Trantor will freeze if it writes to a hard disk using an 8088 CPU. A V20 CPU works with it.
Tandy MS-DOS 3.2, like all DOS versions 3.0-3.3, allows a primary DOS partition of only 32MB. Support for extended partitions was added and standardized in DOS 3.3. Tandy MS-DOS 3.2 does support up to three other DOS partitions on the drive (up to 32MB each), but it requires loading a driver in config.sys on startup and is non-standard. Ultimately I chose MS-DOS 5.00 for its features (edit mainly) and it uses less conventional memory and hard disk space than DOS 6.22. Also, while DOS 3.3's fdisk supports an extended partition up to 736MB in size, it has to be divided into 32MB logical drives from D:-Z:. DOS 4-6 supports a primary partition of up to 2GB, all of which is the C: drive. So MS-DOS 5.00 with a few additions from Tandy DOS (the Mode command, a device driver or two) works just fine. If games start complaining about lack of free RAM (only 624KB is available before DOS due to sharing with the video), then I may have to go back to 3.3.
What kind of games would be played on this machine? Well, all the important PC originals from 1981-1990. I will include any game whose maximum resolution was 320x200x16 and supports Tandy graphics or supports the Tandy sound chip for music and/or effects that does not support an Adlib, Sound Blaster, Roland MT-32 or Game Blaster. Some examples include :
Thexder - Although the game supports an EGA 640x200x16 mode, which is appropriate considering its Japanese origins on the PC-88, it supports Tandy Sound for its music (all of two pieces). Sound effects are PC Speaker only.
Secret of the Silver Blades, Champions of Krynn & Death Knights of Krynn - All support Adlib music, but if you select Adlib you get PC Speaker sound effects. Tandy gives better sound effects than the speaker. Music only tends to be in the introduction to those games.
Games that require an EGA card and do not support Tandy, like Commander Keen, Duke Nukem & Sorcerian) are not going to be on this machine. Similarly, games with a VGA version and an EGA/Tandy version aren't going to be either, unless the EGA version came out first (Indy 3, Monkey Island). Nor would games that support a high resolution color EGA mode (Thexder II - Fire Hawk, SimCity, Zeliard, Silpheed) and sound cards. In short, if there is no real benefit from running the game on a Tandy instead of an IBM PC or clone, then it has no real use in this machine.
The other hardware should be fairly obvious. The Sound Blaster will see little use for its digitized sound and none for its midi or gameport capabilities. Its there because I wanted an Adlib and a Game Blaster in one card. The Roland is the ideal setup, nothing more need be said about it. Chiefly only Sierra's games would have put it to any real use (custom sounds).
The 286xpress Accelerator requires a little explanation. This device is an ISA card that can be used in a Tandy 1000, 1000A or 1000SX. It has an 80286 CPU running at 7.16MHz and 8KB of cache. It has a ribbon cable running from the card's daughterboard to the 8088 CPU socket on the motherboard. It has a spare socket for a 80286 running at 4.77MHz. The 8088 is plugged into the daughterboard. This board does nothing unless activated when DOS boots either by a program loaded in autoexec.bat or a device driver in config.sys. So it will not interfere with PC booter programs expecting 8088 speeds. You can turn the cache off for better compatibility with programs. With cache off, the system is just a little faster or slower than the system running at 7.16MHz on the 8088. With the cache on, it is almost as fast as a Tandy TX or IBM PC AT @ 8MHz. While an TX provides a serial port (freeing up a precious slot) and CPU upgrades fit into the slot (freeing up another slot), even at its slow speed it should still run faster than the SX at its fast speed. So for older games that run like they are on amphetamines unless the CPU is an 8088 running at 4.77MHz, it just isn't as good a choice.
Things to watch out for :
The RCA composite video output hues are somewhat different compared with the IBM PC in CGA modes, causing the colors displayed, compared to the IBM colors, are off. For example, in Winnie the Pooh in the Hundred Acre Wood, Pooh appears in brown on an IBM and blue on the Tandy. You can try to use the tint control on your monitor or TV to adjust the colors, but most TV monitors only allow a shift between red to green, which is not enough to make the colors accurate. A composite monitor designed for computer use may allow a greater range of adjustment. I believe this is present throughout the Tandy 1000s that have composite color output. One game, Indianapolis 500 - The Simulation, by Electronic Arts actually allows the player to select an IBM or a Tandy palette in composite color mode, allowing the proper colors to be displayed with either type of machine. If you use a standard CGA card in the machine, you should be able to get a more accurate IBM color.
The RCA audio output is not turned on by default. (The Tandy 1000/1000A suffers from a similar problem, the EX, HX, TX and later models do not) The default is for all sound to go through the internal speaker. Some programs like Maniac Mansion and Zak McKracken & the Alien Mindbenders fail to recognize that the SX is a little different and do not turn the audio output on. A program called tdyspkr.com can be used in your autoexec.bat to turn the output on to the RCA out and/or off to the internal PC Speaker.
The default 80-column text mode on the Tandy annoyingly uses 225 lines. IBM uses a 200 line text mode. All graphics modes in these machines use 200 lines. In order to get a proper aspect ratio with the graphics modes, the vertical size control has to be set almost to the point where the graphics are almost hidden by the monitor bezel. When you return to the text mode, this winds up cutting off either the top, bottom or both lines of the display. Use Tandy MS-DOS 3.2 mode.com command : mode 200, to fix this. This does not work in the TL machines. You can use the Tandy mode command in a later, non-Tandy DOS.
Tandy floppy disk drives require a ribbon cable without a twist! They also require setting jumpers or switches on the drives to tell the machine which is drive A and which is drive B. On an IBM PC, both drives are set to DS1, and the twist turns the drive at the end of the cable to DS0. If you are using a modern 1.44MB drive in these systems, they are generally soldered to DS1, so they will be the B drive. 5.25" drives should always allow you to set DS0 or DS1. But one of the great things about a Tandy is that they allow you to boot from the B drive by pressing the F3 key at startup. If you have a standard "universal" floppy cable (with 3x pin connectors and 2x card connectors), you have to untwist the cable by prying off the end connectors, flipping the wires around, then snapping the connectors back on again. Tandy did not support high density drives until the RLX and TL/3, but you can use most 1.44MB floppy drives with double density/720KB media.
The EX and SX are the last Tandy 1000s that does not use the floppy connector port to power the drives. The HX, TX and all later Tandys, (inlcuding the SX's replacement, the SL), do run power through the drive cable. If you are using floppy drives on a Tandy 1000 system that do not correspond to Tandy's power-in-drive cable pinouts, you must cut holes in pins 3, 5, 7, 9, 11 and 29, 31, 33 for any portion of the cable going to the regular drive. I used an Xacto knife and a pair of clippers to do the trick, and only small holes are needed. Tandy did this themselves with their cables so an individual could connect a standard 5.25" drive into an empty bay.
In the TL/SL/RL series, there is a way to disable the Tandy joysticks and use an IBM joystick adapter. On the early Tandys, there is no way, you you have to use Tandy joysticks. Tandy used the same joysticks for the TSR-80 Color Computer and the 1000 series. They come in three varieties : the one-button (cheap) black non-centering Joystick, the two-button Kraft-style Deluxe Joystick, and the flight simulator pistol grip joystick (four buttons, only two usable). You can also use a Color Mouse (one-button) or Deluxe Color Mouse (two-buttons) in a joystick port and a special driver. The Deluxe Joystick is virtually identical to the Kraft IBM PC joystick or the IBM PCjr. stick, and can be either set to self-centering or or free floating in one or both axes. There are some subtle differences in the control interfaces between the PC and Tandy joysticks which may manifest themselves in compatibility issues with older games.
Now, while you could use a Tandy Color Computer mouse, this is not an ideal method because of the attention the CPU must spend on the reading the joystick ports. This can slow the PC down. A much better alternative is to use a serial mouse, especially as serial mice are easy to find. So are 8-bit serial cards. Serial cards use IRQs to get the CPU's attention so excess CPU time is not wasted in polling the serial controller's I/O ports. You will need to use an 8250B based serial card, which is typically what 8-bit cards use. I always use ctmouse as a driver as does virtually every other vintage computing enthusiast. Its compatibility is excellent and it only uses 3K of precious memory. In the SX there is no serial port, Tandy fixed this in the TX by replacing the useless Light Pen port with a serial port. (Some games, like the Gold Box games referred to above, do not support using a mouse with Tandy graphics).
Using a printer requires a special adapter cable. For some reason, probably TSR-80 and old-style Centronics printer compatibility, Tandy used card edge printer port on all 1000s until the RL, RLX and TL/3. The ribbon cable would have a card edge connector on one end and a Centronics port on the other end. Fortunately, building a compatible cable should not be a problem, especially if you are connecting it to an IBM compatible printer. One thing to note is that all card edge printer ports are unidrectional and devices that use the port for data transfer in (like a Backpack CD-ROM drive or a parallel port ZIP drive) will not work, even in nybble mode.
Games and programs requiring BASIC may be an issue if they require ROM BASIC. ROM BASIC is virtually unique to IBM PCs and PS/2s of the 1980s, and even highly regarded compatibles like the Compaq Portable failed to run programs that required it. Tandy DOS comes with GW-BASIC, which incorporates the BASIC that would otherwise be in ROM and supports the Tandy graphics and sound capabilities. GW-BASIC may work for some games.
The Tandy 1000SX has two speeds, the default 7.16MHz and the 4.77MHz speed. The latter speed is for compatibility for PC software that was only intended to be run on an IBM PC or XT. Pressing F4 at boot will put the computer into slow mode, which is great for PC booters. The commands mode fast and mode slow can be used in DOS to switch back and forth. Also useful is F1 for mono mode and F2 for TV mode to kill the color text or to make the text more legible on a TV.
With my Compact Flash card, the only noise from the system is from the Power Supply fan. The internal speaker is a large and loud 3" cone, even bigger than the 2.25" cone of the IBM PCs. PC speaker sound can be output to the RCA audio out. If you have a Sound Blaster Pro, which has a 2-pin PC Speaker input, you can connect the header which would otherwise connect to the internal speaker. This allows you to output PC Speaker and Tandy 1000 sound to speakers without having to deal with the RCA port issue and being able to directly control the sound volume.
The Sound Blaster 1.0-2.0 all use DMA1 and do not play nicely with the PSSJ sound chip in the TL/SL/RL, which also uses DMA1. Lockups and freezes are commonplace when digital sound is played. The SX does not have a PSSJ chip, so the issue is not present. However, I have a Central Point Software Option Board, which requires DMA1 in a Tandy system (it can share DMA2 in an IBM system). So if that is installed, the Sound Blaster may not play nicely with it.
The Tandy keyboard is a funny thing. It has 90 keys, and it is much more compatible with the IBM keyboard layout than it first appears. Since an IBM 83 and 84 key keyboard used the numberpad for directional keys, use can use the Tandy's if the dedicated cursor keys are not working in the game. The small shift keys are not much fun, there is no separate * key, the Alt key is in a funny place, and there is no scroll lock equilavent (use Alt Break). Beware the Hold key, it will seem like the machine has frozen until it is pressed again. Its nice that the Num and Caps Lock keys light up, which did not on an IBM PC or XT. The \ key is also less than ideally placed. The fat enter key is far superior to the IBM 83-key keyboard. However, the IBM 83-key keyboard is probably the most solid and clicky keyboard I have ever typed on. By comparison, the Tandy keyboard is mushy and prone to registering a keypress with only the slightest pressure. It does not use rubber dome keys, it has springs in the keys, but still the action leaves much to be desired. PC-compatible keyboards do not work on the Tandy 1000s prior to the TL/SL, but there was an adapter from Tandy that would allow a PC keyboard to work. The Northgate Omnikey keyboards are also compatible with a special cable (which you may have to make yourself).
The SX and TX are the first Tandys that allow their graphics to be disabled if an EGA or VGA board is installed. (The EX and HX can as well, but require upgrade cards with the PLUS adapter). There is a special program that improves the detection of these cards in Tandy 1000s. An MDA or Hercules compatible card should be installable in any Tandy 1000 except perhaps the 1000 and 1000A. You can even install a CGA card in the SX, but some games may detect a Tandy 1000 machine and set their graphics to use the Tandy Graphics Adapter, requiring you to remove it.
On the SX, adding a math coprocessor is as easy as installing it into the empty socket and removing a jumper. The machine came with 384K and was upgradable to 640K by installing eight 256x1 RAM chips into the empty sockets by the drive cage and removing another jumper. There are four switches. Switch 1 is useful if you have a MDA/Hercules card, switch 2 for hard drive controllers that are hard wired to IRQ2, switch 3 and 4 disable IRQ6 and IRQ7, respectively.
The last issues which must be addressed relate to the expansion slots. Original Tandy 1000s did not come provide -5v to the expansion bus. Sound cards like the Sound Blaster 2.0 require this voltage, as do many VGA adapters. The SX has the voltage on the bus, so this should no longer be an issue on the later machines (except for the EX and HX, which also do not have this voltage on the PLUS expansion port). More concerning is that fact that only 10" boards or shorter will fit inside any Tandy 1000 case. The Roland LAPC-I, for example, will not fit, so I used a bare MPU-401 interface box with a small card. Nor will most EMS memory boards. Hard cards may be difficult to come by that will fit.
Tandy 1000s are supremely easy to open, all you need to do is to unscrew two screws from the front or the side and pull the cover forward. Working inside the first generation models is not quite so easy, due to the disk drive cage and the screws used to hold the expansion slots in place. Inside, the screws are all of the hex nut, standard screwdriver types, no Phillips head screws. I use a hex nut on a flexible screw driver handle to get at the screws, and it works pretty well. The expansion slot screws are a nightmare because they are so small and covered a bit by the back plastic piece.
In late 1986, the SX was released in its 2x5.25" drive version for $1,199.00. A similarly configured PC or XT, which did not come with a printer adapter or a graphics adapter, would have cost much more and not have been as much fun. Like the PCjr, it supports 160x200x16, 320x200x16, and 640x200x4. (I think only Deskmate ever supported the last resolution). Unlike the PCjr., it has register level compatibility with CGA, whereas the PCjr. has only BIOS level compatibility. Also, while the PCjr. and the Tandy 1000 support the PC Speaker sound generation, the PCjr. only has a piezo tweeter, while the 1000s have the biggest PC Speaker cone I have ever seen in a compatible. This means that games that tweak the speaker, like Access Software's Realsound games, will sound far superior on the Tandy than the PCjr. The Tandy 1000 does not require device drivers to support more than 128KB, unlike the PCjr. 256KB and greater booter games will work on the former but not the latter. Many games use these graphics and sound capabilities to give great improvements over competing systems. There are several games that support Tandy but not EGA graphics and games that support Tandy sound but not sound cards or midi devices.
PCjr. specific software (almost all of which was released by IBM) may not run on the Tandy or support Tandy graphics and sound. King's Quest and Touchdown Football (PCjr. versions) will not work in anything other than a Tandy 1000 with 128KB of RAM. Fortunately there are Tandy versions available of these games. The near mythical M.U.L.E. port IBM PC was alleged to take advantage of PCjr features but really only supports CGA and PC Speaker sound (but it runs on the jr.). Cartridge software, even when dumped, will not work because it expects to find itself in the D000 and E000 segments.
Unfortunately, the SX requires the 286xpress accelerator board to play those games of the late 80s that run slowly on 8088 machines. The 286xpress is not an easy find as it was very expensive back in the day. Also, finding an ADP-50L is not easy either, as it was a niche product. A fast hard drive is an absolute necessity with these machines. If you cannot find a 286xpress accelerator, then I would definitely recommend a Tandy 1000 TX instead, which has an 8MHz 80286 processor. It is the last system to be truly Tandy 1000 compatible, as the later systems use a PC compatible keyboard and lose composite output.
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