Practical Issues with using the Tandy 1000 TL

This week I have reacquired from a friend a Tandy 1000 TL he once sent me.  I would like to describe my experiences with it, getting programs to work with it, etc.

Floppy Drives :

Tandy really wanted you to use the drives they sold, so they supplied these awkward cables that tended to fit only their drives.  If you have the original Tandy cable, you will not that it does not connect to the floppy header on the system motherboard in the way you would expect.  Instead, it uses the berg connector nearest the the card edge for the 5.25" drive.  That connector plugs into the motherboard, and from that plug the wire comes out at both ends.  The short end has the card edge connector, and the long end has two berg connectors for the 3.5" drives.  The cable may not work with all 5.25" drives.

The next thing to note is that Tandy supplied power to the 3.5" drives through the drive cables.  If you are using a 3.5" drive that does not use the Tandy-power-in-drive method, then you need to cut small holes in pins 3, 5, 7, 9, 11, 29, 31, 33.  Tandy already did this for that end of the cable with a card edge on it, since all 5.25" IBM PC compatible drives use the 4-pin Molex connector.

Additionally, Tandy's cables do not use a twist to determine drive A, B and C.  Instead you must manipulate DS0-DS3 on the drive.  If you use a standard "universal floppy drive" cable, you must untwist the twist. 720KB drives usually have jumpers or switches, as did 360KB and 1.2MB drives.  Modern 1.44MB drives are always set to DS1, so by default they are Drive B:.  The setup program may be able to change that to Drive A:, but you won't be able to use two of these drives unless you figure out how to set one of them to DS0.

Finally, if you use a custom cable, be prepared to insert it "backwards,"  The bit of plastic on one of the ends of the berg connector on modern universal cables is on the wrong side from the Tandy's perspective.  File, cut or dremel it down.

The built-in 720K floppy drive should be a Sony MP-F11W or MP-F17W.  It has a switch on the side to select DS0-3.  It is more or less identical to the earlier Sony 3.5" drives Tandy used except it has a small blue eject button instead of a large "lip" button.

3.5" drives automatically terminate depending on what drive they are, but 5.25" drives have a terminator pack or jumper to set the termination.  Regardless of position on the cable, whichever drive is drive A: must be terminated, and drives B: and C: cannot.  If your 360KB drive is drive B:, remove the terminator.

Hard Drives : Tandy 1000 TL have no hard drive interface, you will need to find one that works in the Tandy.  XT-IDE devices should work fine.  There is a vintage device called the Silicon Valley ADP-50L that uses a faster method for data transfer, memory mapping, than the I/O driven method of the XT-IDE interface.  On the other hand, while the XT-IDE can handle drives up to the DOS Final FAT 16 limits (8GB, 2GB partitions), the ADP card is limited to the Int 13h barrier of 504MB.  There is also the XTA interface that was used with old hard drives, but they only get to 40MB.

Alternatively, you can use an 8-bit SCSI card.  The Trantor T-128 and Rancho Technologies RT1000B will boot in a Tandy 1000 TL.  The more common, yet somewhat slower Trantor T-130B will not boot a device in the TL, but will work if initialized with a floppy drive.  With an external SCSI adapter, you can add floppy drives, hard drives or CD-ROM drives without taking up the precious room in the machine.

Built in Video and Video Cards :

The Tandy 1000 TL's built-in video is a jack-of-all-trades.  It is nearly 100% CGA compatible, supports Tandy 16-color graphics and can also emulate a Hercules card quite well.  It also supports EGA and VGA cards.  You could insert a CGA video card in it, but unless you are looking for composite color output, the built-in video is superior.  Any video card inserted into an expansion slot will "disable" the built-in video.

The video inside the TL and later machines is called Tandy Video II because it supports a special 640x200x16 mode.  Relatively few games support it, but a recent patch provides support for all Sierra 256-color SCI1 and 1.1 games.

With VGA cards, you should run a simple program called VGAFIXC.COM to modify some bytes in the BIOS data area that programs frequently look to to detect VGA.  If you can find a VGA card that can work in an 8-bit slot, there is an excellent utility called VSWITCH that allows you to switch between the built in video adapter (CGA, Tandy, Hercules) and a VGA expansion card.  I use a Cirrus Logic CL-5401 basic 16-bit VGA card I pulled from a Packard Bell.  It works just fine, no jumpers, dipswitches or drivers needed.  With a VGA card, a Tandy system becomes a real jack-of-all-trades when it comes to PC video.

Some games are aware of a Tandy and often do not detect a non-Tandy video adapter, so you may need to force some to work despite their protests if you can with command line arguments or in their setup programs.

You can switch from color (Tandy/CGA) to monochrome (Hercules) by pressing Ctrl + Alt + Shift + V at bootup.

The built in video uses IRQ5 for indicating when the adapter is in a vertical retrace, allowing for rapid screen updates.  It is set by a jumper on E1-E2.  If E2-E3 is set instead, IRQ5 will be available to the expansion slots.  Whether the video uses IRQ2 when IRQ5 is disconnected is debatable.  IRQ5 is typically used by non-Tandy aware hard drive controllers.

Keyboard :

The Tandy 1000 TL only works with keyboard supporting the XT keyboard protocol.  It came with the Tandy Enhanced Keyboard, a standard 101-key autoswitching XT/AT protocol keyboard that works in just about any PC.  It will work in the IBM PC, XT, AT and any PC with a 5-pin DIN or 6-pin PS/2 mini-DIN that supports an XT or an AT protocol keyboard.  It will work in a modern motherboard with a PS/2 port or PS/2 to USB converter.

The TL will also work with an IBM 83-key Model F PC/AT keyboard.  According to the Technical reference, it (and the Tandy 1000 SL) should also work with a 90-key Tandy 1000 keyboard, but it requires an adapter because the Tandy 1000 keyboard uses an 8-pin DIN and the Tandy 1000 TL keyboard port is a 7-pin DIN.  I tried making an adapter, but no key presses were registered.  The TL/2, SL/2 and later machines do not have a 7-pin port, so this functionality cannot be used, even if it exists, in these machines.

Case :

The case for the later Tandys are all really easy to remove.  Just unscrew one screw on each side and pull the sides out a bit, then up, then forward.  Unlike the earlier Tandys, you don't need to disconnect the keyboard or the joystick ports, which have been relocated to the back of the machine.

Inside the machine is easier to work in than the older models.  There is no internal shielding to remove to get at the innards.  The TL uses a sheet metal cover, unlike the TX and earlier models which used plastic.  The screws for the expansion slots are small phillips head screws, and the plastic on the back has indentations to allow for easy screwdriver access.  The left 3.5" drive bay can be removed by unscrewing two screws on the front metal chassis and pushing the bay back until the clips clear.  The 5.25" bay requires drive rails.  I am not sure whether modern drive rails will work.

The front bezel may have the left 3.5" drive cutout covered with a plastic panel.  Once the panel is removed, you can install another floppy drive that conforms to the shape of the cutout.  If it does not, or you wish to use some drive with a faceplate, you will need a dremel.

Serial :

There is one 9-pin serial port on the back, and it uses a 8250B UART.  It is set to COM1.  However, the serial hardware has been incorporated into the PSSJ chip, so it may not be as robust as a card with a discrete chip.

Game Ports :

There are two 6-pin DIN game ports on the back of the machine next to the keyboard sockets.  Unlike the game ports of the TX and earlier models, you can disable the built-in game ports of the TL and later machines in software.  The game ports in the TX and earlier machines have to be disabled by cutting a pin or two on one of the ICs on the system board.

Parallel Port :

The Tandy parallel port has been covered in more detail in another post.  In the TL, there is a setup setting for output enable.  This should corresponds to bit 5 at port 37A, allowing for bidirectional mode.  However, as the Tandy parallel port in any model with a PSSJ chip (except the TL/3 and RLX) is missing one of the printer select lines, it may not work with any device requiring bidirectional parallel port mode.  The other printer select line has a jumper, E4-E5, to connect it from the card edge to the PSSJ.

Conventional Memory Upgrade :

The TL can be upgraded from 640K to 768K by inserting four 64Kx4 (120ns or better) chips into the four unpopulated memory sockets on the motherboard.  This extra RAM will allow you to enjoy a full 640KB of conventional memory without the onboard video taking a portion of it.  However, this extra 128K cannot be used for any other purpose, it is solely dedicated to the on-board video.

Expanded Memory :

Only a few Expanded Memory boards will work in the TL, and this is mostly due to the fact that there is only room for 10" cards.  Most Expanded Memory boards run the full 13".

Real Time Clock :

The TL uses a Dallas 1215E RTC which is powered by a coin-style battery, a CR2032.  The built in DOS-in-ROM will handle keeping the system date and time up to date, a separate driver is not needed.

CPU Upgrades :

A math coprocessor socket is available in the TL.  The 80286 CPU is socketed in a 68-pin PLCC socket under the left 3.5" bay.  It should only be removed with a PLCC extractor and after the bay above has been removed.  There are 386 and 486 upgrades which can plug into these boards and offer up to 2x the performance of the original 8MHz 80286.  The built-in video performance will not improve.  I have one called the IO Data PK-X486/87SL, which is a Japanese product intended for an NEC-9801 machine.

While the accelerator is usually a good thing, I have encountered two problems with the one I am using.  First, the floppy drives simply will not respond, no matter how the machine is slowed down.  Second, the audio recording function is speed-sensitive in the TL, so audio will record too quickly using Deskmate.  The TL/2 should fix this problem with a double-buffered chip.  I understand that Improve Technologies Make-it-486 will also work in the TL.

Built in Sound and Sound Cards :

The TL comes with the Tandy PSSJ sound chip.  It provides for Tandy 3-voice sound and digital audio input and output through the internal speaker.  The speaker has a volume control, an earphone out and a line/mic in.  Do not connect a Line Input without first setting the jumper to E7-E8.

The digital audio output function sits on DMA1 and doesn't like other sound cards, like a Sound Blaster, to use DMA1.  It also uses IRQ7.  A Mediavision Thunderboard allows you to disable the DAC, at which point is functions like an Adlib with a gameport (and without MIDI interface).  Additionally, a Pro Audio Spectrum 16 and a MedixTrix AudioTrix Pro require software initialization before functioning, so they will work with the PSSJ.

Sound Blaster Pros and early Sound Blaster 16s only work with the PSSJ when set to DMA3.  Earlier Sound Blasters are hard wired to DMA1.  The DMACTRL jumper on some Sound Blaster 2.0s and Pro 1.0s will not solve the problem, nor will removing the jumper from DRQ1, since DACK1 is still wired.  The second greneration Sound Blaster 16s, which use diagnose.exe or sbconfig.exe to set their IRQ and DMAs should work.  For a solution for the ISA PnP Sound Blaster 16s, look here : http://www.vintage-computer.com/vcforum/showthread.php?38484-ISA-XT-Sound-card-list.

The DAC in the SL and TL were rather speed sensitive.  Essentially an audio sample played back in one machine would be too fast or slow in the other machine unless the program adjusted itself for the system speed.  This is not an issue in the TL/2 or SL/2 or later computers because the DACs on these computers are double buffered.

DOS-in-ROM :

The TL comes with the basic core of Tandy DOS 3.3 in ROM.  This is very helpful when you are trying to run DOS programs off floppy disks, you don't need a disk with COMMAND.COM in the drive.  If you have no hard drive installed, then the DOS-in-ROM becomes drive C: if you have 1-2 floppy drives, and drive D: if you have three.  If you have a hard drive installed, it will be drive C: or D: and the ROM drive will be drive D: or E:.  Here are the contents of the ROM drive :

 Volume in drive D has no label
 Directory of  D:\

AUTOEXEC BAT       20   6-15-88   1:00p
AUTOMEM  COM     1962   6-15-88   1:00p
COMMAND  COM    25612   6-15-88   1:00p
DESK     COM       77   6-15-88   1:00p
DISKCOPY COM     6264   6-15-88   1:00p
DRVR8530 MOD     6652   6-15-88   1:00p
FORMAT   COM    11681   6-15-88   1:00p
NETBIOS  MOD     8092   6-15-88   1:00p
NETLOAD  COM      485   6-15-88   1:00p
RESTART  COM      209   6-15-88   1:00p
       10 File(s)         0 bytes free

IBMIO.SYS and IBMDOS.SYS or IO.SYS and MSDOS.SYS should also be present, but hidden.

The TL came with Tandy MS-DOS 3.3 on one 720KB disk.  The disk contains all DOS programs on one disk and is fully bootable.  Important programs on the disk are SETUPTL.COM, which allows you to enter the setup menu, BASIC.EXE and BASICA.COM, which grant you access to GW-BASIC, and MODE.COM, which allows you to control Tandy specific features like Mode Slow (for 4MHz operation).  Unfortunately, the MODE.COM included in the Tandy TL disks has a bug where the MODE 200 command does not work in the 80-column text mode.  Take the MODE.COM from the RL system disks and restore that feature.

If you upgrade to MS-DOS 5.0 or better, you will lose the ROM drive.  In this case, you will need a standalone version of Deskmate.  Standalone Deskmate doesn't come with the music or sound programs, so you may need to rescue them from the TL Deskmate disks.   Additionally, you should use drivparm in your config.sys for every floppy drive. drivparm=/d:0 /f:2 for a 720KB 3.5" drive and drivparm=/d:1 /f:0 for a 360KB 5.25" drive.

Deskmate :

The TL came with Deskmate 3.0, partially in ROM and the rest on two 720KB disks.  The main executable is DESK.COM on the ROM drive and it will allow you to enter the basic graphical shell.  To use programs, you need to install them off the floppies, or change the directory to where the programs are located on your hard drive.  The ROM Deskmate may be necessary to access the music and sound programs, which use the PSSJ sound chip.  The Deskmate draw program will use the 640x200x16 mode.  If you have a VGA card installed, you will need a VGA Deskmate driver.  Deskmate 3 works well with serial mice supporting the Microsoft serial mouse protocol.

Setup Utility :

The basic setup utility is displayed by using SETUPTL.COM.  SETUPTL /A brings up the advanced menus, and SETUPTL /F restores the settings to the factory defaults.  

The basic setup functions are identified in the TL Practical Guide.  If you have a hard drive, there is little need to change the usual settings.  You will probably want to set the Initial Start-up Program to MSDOS instead of DESKMATE.  It may not seem intuitive, but if you have a hard drive with MS-DOS 3.3 on it, the setting for Primary Statup Device should remain ROM.  You should also definitely Check for Autoexec.bat and Config.sys on Drive C:  If you have upgraded your DOS to version 4.00 or later, then you must select DISK as the primary startup device.  

As far as the advanced menu goes, you won't find much of interest here.  The first screen is Diskette, and the TL should automatically detect the number and types of floppy drives you have.  Running the basic utility usually works to automatically recognize a new drive.  If it doesn't, you can try setting them here.  The second screen is System Startup, and everything here can be found on the basic menu except for Video Memory.  The maximum amount of video memory is only an issue when you don't have the 768K upgrade.  The default value is 64K, which is sufficient for the 640x200x16c graphics mode.  The maximum is 128K, and if you have the upgrade you can set it to that amount because that memory can't be used for anything else.  

The third screen is BIOS Machine State.  There are off/on selections for Hard Disk, Parallel, Video, Diskette, Serial Chip Selects and Parallel Output Enable.  All default to on.  The Hard Disk Chip Select is useless as there is no hard drive interface in the TL, perhaps it was meant for the TL/2.  The Diskette Chip select apparently does not work, you will need a program called nofloppy.com, available here, http://www.oldskool.org/guides/tvdog/1000TL.html to disable the built-in floppy controller.  Since the on-board video is disabled when a VGA or EGA card is installed, the video chip select is more harmful than helpful.  Parallel Output Enable apparently does not make the built-in parallel port bidirectional, at least to devices that weren't sold by Tandy.

Later on that page, there are Wait State cycle options for Internal Memory, External Memory (Expanded Memory), CPU I/O Cycle, DMA Cycle, 16-bit Video.  The defaults, 0, 3, 3, 1,1 are safe values and probably should not be changed.  Last is the OSCIN frequency, which defaults to 24MHz but can be set to 28.636360MHz. I think the OSCIN frequency has something to do with the PSSJ chip.

The next two screens have to deal with network adapters, and unless you have the specific Tandy adapters the ROM expects, then these screens are useless.  The penultimate screen is International and lets you select the language, country code, keyboard type and code page.  If you live in the US, there is no need to change any of these settings.  The final screen is Usable Programs, and let you specify whether each program on the ROM disk can be used.