Sunday, July 22, 2012

Observations on 8-bit Video and Sound Cards

8-bit Video Cards

In an IBM PC, Portable or XT or a clone or a Tandy 1000, these are your options.  I will talk about the IBM cards and note possible differences with clone cards.

IBM Monochrome Display Adapter

This card can only display 80-column by 25-row text, and uses a special TTL monochrome monitor.  The official monitor is the IBM 5151 Display, but clones exist.  Not especially useful for games as the next card.  Full-length 13" card (as are all IBM 8-bit Video cards), 4KB Video RAM, enough for one page only.  Can be used with a CGA card in a dual monitor setup.

Hercules Graphics Adapter

Can do everything the MDA can and more.  The "more" is a 720x348 monochrome graphics mode that tons of 80s game use.  The Hercules-brand cards tend to be 13" full-length cards that do not fit inside Tandy 1000s and other machines with card clearance issues.  Many EGA cards include Hercules functionality, as do the Tandy 1000 T/S/RL machines.  Many people back then and some vintage enthusiasts today use a CGA card with a color monitor and a Hercules card for text on a monochrome monitor.  This avoids CGA snow in text modes.  64KB Video RAM, usually 32KB used (so-called Half-mode).  Full-Mode, using 64KB RAM, will conflict with CGA and later cards.  

IBM Color/Display Adapter

16KB Video RAM
Displays CGA Snow
Uses B8000-BFFFF
Only fits in an 8-bit slot, has a skirt
Requires a functional 14.318MHz OSC signal for composite signal
Has two solder points to wire a jumper to select the "thin font".
Early cards display a slightly different color arrangement in composite color mode.  If your text has red and blue fringes, you have an early card.  If the text has orange and blue fringes, you have a later card.  
Early cards only display four shades of gray on a monochrome/black&white TV or composite monochrome monitor.  Later cards display 16 shades of gray.  
Supports an RF adapter and a light pen via pin headers.  

Clone cards function similarly to IBM's, but their fonts are likely to show differences and they may lack support for a light pen or a header for an RF adapter.  I have an Epson clone which does not have a discret MC6845 CRTC and thus is not quite as compatible with the IBM CGA.  Early clones tend to have the 8-bit skirt, later clones tend to be shrunk down.  Official monitor is the IBM 5153 Color Display, which supports 200 lines in 16 colors.  It can work with an IBM 5154 Enhanced Color Display, Tandy CM-4, CM-5, CM-10 or CM-11.  The IBM PC Portable has a built-in 9" amber monochrome screen and it requires a CGA card with composite output.  

ATI's Small Wonder cards combine CGA and Hercules support, and they are probably not alone.

IBM EGA Adapter

Uses IRQ2 for vertical sync
64KB on Motherboard, requires separate Expansion daughterboard to add 192KB for the full 256KB.  128KB required for 640x350x16 graphics.  (Clones tended to have 256KB on board)
Daughterboard uses standard 64Kx1 chips
Can be set to use alternate 2xx I/O addresses via jumper
Can support light pen
Must use jumper and dipswitches to set  monitor type, can use IBM Monochrome, IBM Color and IBM Enhanced Color displays
Can be used with an MDA card in Color mode or a CGA card in monochrome mode
No Hercules support
Can fit in 16-bit slot, but has skirt otherwise
16KB BIOS ROM, mapped C0000-C3FFF (Clones often used 32KB, mapped to C7FFF)
RCA jacks are useless without a Feature Board (IBM never offered one)
Only IBM 8-bit Video Card with Jumpers and Dipswitches.

Some clone cards utilize the 16-bit ISA connector, support non-standard line modes, and offer Hercules compatibility.  IBM 5154 Enhanced Color Display is the official monitor, supporting 350-lines and 64 colors.  This monitor and its clones are pricey and many people use a CGA monitor.  Remember to set the dipswitches on the bracket appropriately for a 200-line monitor.  It can also use MDA monitors if you set the switches appropriately.

IBM VGA Adapter

Unlike other IBM cards, this card is full length but has a lower profile, width wise.  No skirt.
Uses IRQ2 for vertical sync.
Designed to upgrade IBM PS/2 Model 30 systems to VGA, works fine in IBM PC, XT, AT, XT-286.
Officially called the IBM PS/2 Display Adapter
Will not fit inside an IBM PS/2 Model 25.
Finicky with 3rd-party motherboard
Uses EPROM to store VGA BIOS (32KB EPROM, 24KB used).
Has two BERG-strip pin headers, functionality unknown
256KB video memory, no further upgrades
24KB BIOS ROM, mapped C0000-C5FFF (Clones almost always use 32KB)
8KB of scratchpad memory, mapped C8000-C7FFF (6KB) and CA000-CA7FF (2KB)  Clones do not have this and this mapping is often an annoyance with other cards that can use the CA000 region.  
Jumperless, no lightpen support

Many 16-bit VGA cards can work in an 8-bit slot.  The Paradise PVGA1A chipset is a good choice, but even some Tseng ET4000AX boards will work.  Don't expect to set speed records.  

8-bit Sound Cards

There are relatively few 8-bit Sound Cards, in fact these are really your only choices for games :

AdLib Music Synthesizer Card

The first sound card, first revision has a 1/4" audio jack, second revision a 3.5mm mini-jack.  OPL2 FM Synthesis.  Noisier than a Sound Blaster.  May be necessary to use an AdLib in a Tandy 1000 T/S/RL due to those systems not playing well with a Sound Blaster.  Clone boards will work the same if they use a Yamaha YM3812 OPL2 chip and its Y3014 DAC.  

AdLib Gold 1000

Backwards compatible, adds 8-bit and 12-bit DAC functionality but its midi interface is not MPU-401 compatible in any way.  No Sound Blaster compatibility.  Has header for optional surroundsound daughterboard.  Dune makes use of the daughterboard and only supports stereo OPL3 FM Synthesis on this card.  Card is rare, daughterboard extremely rare.

Covox Sound Master

Uses GI AY8930 for music and 8-bit DAC/ADC.  No compatibility with other cards.  Has some near-exclusive game support.  Also supports two Atari-style digital gamepads.  Virtually impossible to find.

Covox Sound Master Plus

AdLib compatible OPL2 FM.  8-bit DAC, but not completely compatible with the previous card as some games use the AY8930 for DMA.  Ditto on findability.

Covox Sound Master II

AdLib compatible OPL2 FM, 8-bit DAC.  Basic Sound Blaster compatibility.  Somewhat more common.

Creative Music System/Game Blaster

Uses 2 x Phillips SAA-1099 (CMS-301) for music.  Certain CMS/Game Blaster cards will not work with Sound Blaster cards with C/MS chips due to the custom board detection chip on these boards.  Only way to get trouble free CMS sound on Tandy 1000 T/S/RL systems due to DMA conflict between Sound Blaster and Tandy DAC.  Very rare.  

Creative Labs Sound Blaster 1.0 & 1.5

1.0 has CMS chips onboard.  DSP in 40-pin socket.  Typically came with v1.05, could be upgraded to 2.0.  2.0 adds auto-init DMA, which was necessary to meet Windows MPC specification.  Regardless of DSP version, DAC limited to 8-bit @ 22.050kHz playback.  AdLib compatible.  MIDI port is not MPU-401 compatible, even in UART mode.  Removing the DRQ1 jumper will not solve problems with Tandy 1000 T/S/RL systems.  The 1.5 has 2 sockets for CMS chip upgrade, otherwise identical to 1.0.

Creative Labs Sound Blaster 2.0

DSP v2.01 adds 8-bit @ 44.1kHz DAC playback.  Loses alternate I/O selections compared with 1.0, but many games expect the Sound Blaster at I/O 220-22F.  CMS upgrade requires a Programmable Logic Array (PAL) chip, which has been reverse engineered using a Generic Logic Array chip (GAL).  The GALs of today only work on rev. 3 and rev 4 SB 2.0s unless you use one from National Semiconductor, which are the only ones that work on boards without a rev.  They will not work reliable on rev. 0 (no revision) boards, so avoid those if you intend to upgrade.  Cards with a CT1336A Bus Interface Chip will not work with the CMS upgrade, even with a true Creative Labs' PAL.  Very short card for its time.  

Creative Labs Sound Blaster Pro 1.0

Although the Sound Blaster Pro cards have a 16-bit connector, all it does is allow you to select IRQ10 or DMA0, both very unpopular resource choices.  They work just fine in 8-bit systems and you can dremel off the 16-bit portion of the card edge with no ill effects.  The Pro supports stereo FM with 2 x OPL2 chipsets and 8-bit @ 44.1kHz DAC.  It also introduces a hardware mixer, which some games use to create stereo sound.  Virtually useless proprietary Panasonic CD-ROM interface on the common CT-1330, but it does not take up extra resources.  The Pros allow you to select DMA3, which means they can work with the Tandy 1000 T/S/RL series.  They have a 2-pin header to connect the PC Speaker header on the motherboard.  Usually the motherboard header is a 4-pin strip, but a simple "rewiring" of a CD audio cable works for me.  The PC Speaker will sound louder through the Pro than through systems with a piezo tweeter or a tiny speaker.  

Creative Labs Sound Blaster Pro 2.0

See above, but uses an OPL3 for stereo FM.  There are games that prefer the dual OPL2 setup, and for the later games that may utilize OPL3 features, they almost always sound better with General MIDI.  Shorter than the Pro 1.0 and less noisy sound output than the early Sound Blaster 16s.  CT-1600 is the most common and uses the Panasonic CD-ROM interface.  CT-1690 has a non-bootable SCSI interface which works with SCSI CD-ROMs.  

Innovation SSI-2001

A MOS 6581 SID on a card with a gameport.  Extremely rare.  I have seen two pictures of these cards, and both use 6581R4 chips, not 6582/8580 (would need a 9v converter on board).  A 6581 requires a +12v power source, which the ISA bus provides.  The SID chip's 29 registers are mapped directly on the I/O bus starting at 280, 2A0, 2C0 or 2E0.  The SID should be clocked at .894MHz.  The filter will sound different, as the Caps on the C64 used 470pf and the SSI board uses .01uF.  Extremely rare.  

Mediavision Pro Audio Spectrum (PAS)

AdLib compatible, no Sound Blaster compatiblity.  Requires loading MVSOUND.SYS in CONFIG.SYS for card to work.  8-bit @ 44.1kHz DAC support.  SCSI CD-ROM interface.  Better noise characteristics than any 8-bit Sound Blaster.  Stereo FM using 2 x OPL2 chipsets.  There are games from Sierra that support this card for stereo FM music that do not support the Sound Blaster Pro.  The MIDI interface has  no MPU-401 compatibility.  

The PAS can emulate the PC Speaker without having to route the sound from the motherboard.  This is weird, however, since there is a header for the analog PC speaker output from the motherboard on the card. 

The jumper settings for the original, 8-bit Pro Audio Spectrum are hard to find online and not marked on the circuit board.  Look here, which also gives the pinout for the CD Audio input header : 

Mediavision Thunderboard

AdLib and Sound Blaster 1.5 compatible clone (no CMS) with a volume wheel.  Some games have a Thunderboard install option for better compatibility.  Claims dynamic filtering for better output quality.  Supposed to be reported as a 2.0, presumably because it supports auto-init DMA as does a SB 1.5 with DSP v2.01.  The Thunderboard can disable the FM via jumper to work alongside the PAS and provide Sound Blaster compatibility to the Pro Audio Spectrum.  (I assume you can do the same thing on a real Sound Blaster by removing the YM3812 chip.)  The PAS16 would use the Thunderboard chipset for Sound Blaster compatibility.  Do not use in a Tandy 1000 T/R/SL because the DMA channel cannot be changed or disabled.  Interestingly, for a Sound Blaster clone it does not support MIDI output of any kind from the joystick port.  There is a version called the Thunder and Lightning that does support MIDI output and the capabilities of an SB2.0, licensed from Creative.  Its jumper settings are here :

Roland MPU-401 + MIF-IPC or MIF-IPC-A

Strictly a MIDI interface, but if you need 100% Roland MPU-401 compatibility, your choices are limited.  The large external box contains all the major circuitry, the MIF cards are simple bus adapters and can easily be replicated.  There were several ROM revisions, with the final revision being v1.5A.  This revision is used in the MPU and LAPC-I cards.  The MIF-IPC is supposedly not compatible in AT-bus systems (16-bit ISA bus systems), while the -A card adds AT-bus compatibility.  I/O address and IRQ2 usage cannot be changed without cutting traces and soldering wires or a dipswitch box.  The box can be used in many other systems (Apple II, Commodore 64) with the appropriate interface card.  Connectors include 2 MIDI OUTs.


Virtually the same as the above, although this time the circuitry is on the card and the external box is just for the connectors.  The -T loses the Sync Out (useless for gaming) but allows changing the I/O and IRQ usage without physically altering the card.  Connects to the external box via a DB-25.

Roland LAPC-I

Provides the exact synthesis of a Roland CM-32L (MT-32 rev. 1 + 33 extra sound effects) plus a Roland MPU-IPC and selectable I/O and IRQ usage.  Has a headphone and two RCA jacks.  A DA-15 connector connects to its MCB-1 box for interfacing with extenal devices, which was sold separately.  A Gameport-to-MIDI adapter cannot be used unless pins are altered inside the cable.  Is a full-length card and requires a -5v power on the ISA bus.  Modern ATX power supplies (2.0 and above) do not supply the appropriate voltage.  In a pinch you could wire in a 7905 to convert it down from the -12v line, which is still supported.  Uses the CM-32L Control ROM, v1.0 (EPROM) or v1.2 (Mask ROM).  

Roland SCC-1

Provides the exact synthesis of a Roland  CM-300 (SC-55 base) plus a Roland MPU-401 interface, but only 1 MIDI OUT and 1 MIDI IN.  MIDI OUT requires a special mini-DIN to DIN cable.  Stereo speakers and RCA outputs.  The SCC-1 supports 317 patches, the SCC-1A card supports 354 (SCC-1B is a marketing term for an SCC-1A and the Ballade software).  Capital tone fallback (see my previous post about Unique PC Hardware) feature is not supported in the SCC-1A.  MPU-401 uses ROM revision 1.5B.  

Roland MPU-401/AT

The MPU-401AT uses the same MPU-401 features and ports as the SCC-1, but only has a 26-pin waveblaster header.  It has no on-board synthesizer by default, but can use any daughterboard that will fit on it.  Roland offered two, the General MIDI (with extra drumsets) compatible SCB-7 (a SC-7 derivative) and the General MIDI/GS compatible SCB-55 (a SC-55mkII derivative).  I have used a Yamaha DB50XG on the board without problems.  The audio output is superior than a Sound Blaster.  

There has been confusion between the labels SCB-7 and SCB-55 and SCD-10 and SCD-15.  The former two names identify and are silkscreened on the hardware boards, the latter refer to the product bundle with the box, software and manuals.  The bundle with the SCB-55 and MPU-401AT ISA card is called the SCM-15AT.  

Unfortunately, the MPU-401AT is extremely small and virtually all daughterboards will extend well-beyond the edge of the board.  Longer boards have four holes for the daughterboard standoffs, but this board only has two holes for standoffs.  The end result can be wobbly.  Finally, the name and manual for this card indicate that it is not PC or XT compatible, but because the card was released in 1995, those systems were seen as obsolete.  The card probably works fine in 8-bit XT compatible machines.  Finding standoffs of the right height will likely prove to be a time consuming task.  

All three Roland cards with sound synthesis capabilities can accept MIDI data from a separate computer.  In this sense, the cards can act as external modules.  


Anonymous said...

Do you have any more information about MediaVision's Pro AudioSpectrum cards like technical documentations, or even an sdk? I'm asking because the only site that has those images about the Pro AudioSpectrum and Thunderboard cards is this one.

Please let me know, because I'm really interested...

Thank you for your very informative blog posts!
Have a nice day!

Anonymous said...

Had 486dx50, amd k6 200, celeron 300a/bh6 with Yamaha SW60XG, GUS ACE and Thunderboard (for adlib)... To my ears, game music has not marked improved from those days - almost similar developments as in pop - the music has got less complicated and involving.

Yamaha put out a VST synth that sounds identical to that card and after some tweaks the DosBox sounds like GUS ACE (pan table was not correct). Earlier got MT32, SCC1, SC55mk2 from bay to compare against the software versions. I'd say the software MT32 is good enough, the Virtual Sound Canvas is better than windows midi synth but not good enough to my ears.