Do you desperately want a sound card for playing games on your Micro Channel-based IBM PS/2 computer--a system designed for serious business purposes? Do you not want to pay the ludicrous auction prices for the rare Sound Blaster MCV cards? Well, despair no longer: the Snark Barker MCA has arrived!
The Snark Barker MCA is a Sound Blaster-compatible sound card designed specifically for computers that use the Micro Channel bus. It supports Ad Lib synthesis, digital sound playback and recording, a standard PC joystick, and SB MIDI.
All of the components are readily available. In the bill of materials, Mouser part numbers are listed where available. The Yamaha synthesis chips may be obtained from a variety of sources in China, but they are not guaranteed to work, so I recommend getting 1 or 2 extras just in case. The same goes for the NE558. Note: A user reports that a Signetics NE558 with a date code of 8825VI that seems to be commonly available from China does not actually work. If you can't find any working 558 chips, try building my replacement that uses four 555 chips.
Please note that the 0.1" header pins are not listed on the BOM. They are standard breakaway headers. Headers J2, J4, J5, and J6 are optional and only useful for people who want to connect a logic analyzer to the bus for CPLD debugging.
The CMS chips U14 and U15 should not be installed since CMS functionality is not implemented at this time. Other devices listed as "DNI" are to be left empty with no component soldered in place.
Logic chips are all specified as AHCT, but ALS or ACT may also be used. Do not use LS or HCT devices, particularly for U2, since Micro Channel is a much faster bus than ISA and this logic is not quite fast enough to meet the timing margins. Bipolar families like F or S devices use excessive amounts of power but can be used in a pinch.
This is a 4-layer board. The order of the two inner layers does not matter, but typically it goes F_Cu, In1_Cu, In2_Cu, and B_Cu. The board dimensions are 11.5 inches (292.1mm) by 3.475 inches (88.265mm).
When ordering the board, you must specify a card edge bevel of 20 degrees (details of the bevel are included in the Dwgs.User layer). This is not optional! The contacts in the Micro Channel socket are easily bent if you attempt to insert a card with no bevel. Don't believe me? See this page.
Ideally you should use selective gold plating (hard gold) for the edge fingers, but this can get expensive for small orders. ENIG will work but the gold will rub off fairly quickly.
For the soldermask color, pick whatever you want!
I recommend soldering the CPLD (U31), the voltage regulator (U32), and the associated surface mount capacitors before you solder in the remaining components. You can do this by hand with a pencil iron or you can use a reflow process, but be aware that the board is too long to fit in the small hobbyist reflow ovens.
Be sure the CPLD is soldered in the right way around! Compare it with my photo of the card to be sure you have it right!
Inspect the CPLD's solder joints carefully with a microscope to make sure you don't have any bad connections or solder bridges. This can save you a lot of grief later on.
Install sockets for the Yamaha chips U9 and U10 in case you get one that doesn't work and need to replace it.
MCA brackets are no longer available. You have a few options:
- Remove the brackets from an existing card, like a token ring card or something common
- 3D print the bracket
- Use the card without a bracket at all
If you want to print your own brackets, here are STL files of the front panel bracket and the rear bracket.
For best results, use high quality filament and a layer height of 0.16mm or better. If you print using blue filament, the color will match the original IBM brackets.
The front bracket should be oriented so that the front face of the bracket is facing towards the bed of the printer. The rear bracket should be oriented so its large flat spot (parallel to the card) faces the bed.
To secure the bracket to the card, you need two screws, and you have several options:
- 2-56 pan-head screws, 3/16" long, McMaster Carr 91772A076 or similar. These work but aren't the strongest.
- Number 2 thread forming screws, 3/16" long, McMaster Carr 99461A710 or similar. These should grip the plastic tightly (TODO: untested).
- There may be equivalent metric options but this requires experimentation. Please let me know if you find a fastener that works well.
There are two ways to get a programmed 80C51 chip for the Snark Barker MCA. One is to purchase a SB 2.0 DSP chip from China and put it in a 44-PLCC to 40-DIP adapter. This works fine and provides the largest feature set.
Another option is to buy a blank Atmel 89S51 (as listed in the BOM) and program it with this HEX file.
The Snark Barker MCA uses a CPLD (Complex Programmable Logic Device) to interface between the Micro Channel bus and the rest of the card's digital logic. This CPLD implements port IO, interrupts, DMA, and the card setup and POS (Programmable Option Select) systems.
The CPLD must be programmed with the bitstream before you can use the card. You can find the bitstream here.
I've had good luck using the Linux command line program 'xc3sprog' with a FTDI FT2232H Mini Module datasheet here.
Wiring for the FT2232H mini module:
| Point 1 | Point 2 | Description |
|---|---|---|
| CN2 pin 1 | CN2 pin 11 | V3V3 to VIO strap |
| CN3 pin 1 | CN3 pin 3 | VBUS to VCC strap |
| CN2 pin 3 | CN3 pin 12 | V3V3 to VIO strap (2) |
| CN2 pin 5 | JTAG cable pin 6 | V3V3 to Snark Barker (optional) |
| CN2 pin 2 | JTAG cable pin 5 | GND |
| CN2 pin 7 | JTAG cable pin 4 | AD0, aka TCK |
| CN2 pin 9 | JTAG cable pin 3 | AD2, aka TDO |
| CN2 pin 10 | JTAG cable pin 2 | AD1, aka TDI |
| CN2 pin 12 | JTAG cable pin 1 | AD3, aka TMS |
You need to provide external power to the Snark Barker through the 3.3V wire on the programming header. The optional wire does this, or you can use a bench supply.
I obtained xc3sprog here. You can compile and run this program on a Raspberry Pi to use the Pi GPIO lines instead of the FTDI mini module. In my case, I chose to patch it (TBD) to remove references to the Pi GPIO library and ran it on a regular Linux PC.
Using the FTDI mini module, programming is quite simple. Connect the cable to the assembled Snark Barker board, then run the following command. You can do this with just the CPLD, programming header, and surface mount capacitors--there's no need to have any of the other components soldered in place for this step.
xc3sprog -c ftdi -v mcadlib.jed
If you run into issues with the cable not being detected, check your udev rules. In theory you could run xc3sprog as root, but that's bad practice. ;)
If you're feeling particularly masochistic, you can try building the CPLD project using the Xilinx ISE Webpack tools. Because the ISE Webpack only supports Ubuntu 14.7, it's simplest to run the program from a Docker container. I use docker-xilinx.
This isn't meant to be an exhaustive tutorial on how Micro Channel works (you can find a tutorial here). Functions provided by the CPLD include:
- Card setup and POS
- Address decoding logic
- Bus logic interface to the YM3812
- Wait state logic for the YM3812 interface
- Interrupt logic
- DMA state machine including arbitration logic
Each card implements several 8-bit registers (POS registers). Two of these registers are fixed and implement the 16-bit card ID value, which is how the BIOS and the reference disk software identify the card. The remaining POS registers can be used for any configuration-related function and are designed to replace configuration jumpers. The meanings of each register bit are up to the card designer, with the exception of a reserved bit that is used by the BIOS to enable or disable a card; this way, the BIOS can resolve conflicts automatically. Typically POS register bits control IO and memory address assignments, IRQ lines, and so forth.
The CPLD implements the two required ID registers as well as two additional POS registers. The first contains only a single bit -- the card enable signal. The second register controls the IO port setting, the IRQ and DMA channel settings, and the joystick port enable bit.
When you add a new card to a MCA bus system, the BIOS detects the new card and requires you to run the reference disk configuration program. This program searches for an ADF file associated with the new card. The ADF file is human-readable text that tells the BIOS which I/O address, IRQ, etc match up with each POS register bit. The reference disk program uses this information to find a configuration for all the cards in the computer so that none of them conflict with each other. When it's done, it writes the raw POS register values along with the card ID values to the battery-backed SRAM on the motherboard.
The Snark Barker MCA has been tested on some models of PS/2. More to be added as people provide test reports.
| Computer | Model | CPU | Compatible ? |
|---|---|---|---|
| IBM PS/2 Model 50Z | 8550-031 | 80286-10 | Yes |
| IBM PS/2 Model 55SX | 8555-X31 | 486SXLC2 | Yes |
| IBM PS/2 Model 56 | 9556-KB6 | 80486SLC2-50 | Partial(1) |
| IBM PS/2 Model 70 | 8570-E21 | 80386DX-16 | Yes |
| IBM PS/2 Model 70 | 8570-B21 | 80486DX2-50 | Yes(1) |
| IBM PS/2 Model P70 | 8573-061 | 80386DX-20 | Yes |
| IBM PS/2 Model P75 | 8573-401 | 486DX2-66 | Yes(5) |
| IBM PS/2 Model 80 | 8580-071 | 80386DX-16 | Yes(4) |
| IBM PS/2 Model 95 | 8595 | 486DX2-50 | Yes(1) |
| IBM PS/2 Model 95 | 9595 | Pentium-90 | Yes(3) |
| NCR System 3400 | 3433 | 486DX2-66 | Yes |
| NCR System 3400 | 3421 | 386SX-20 | Issues(2) |
Note 1: See the Machine Specific Notes section below for more details about this configuration.
Note 2: Some problems reported with the NCR 3421 possibly due to a conflict with the onboard SCSI. Further investigation is needed.
Note 3: The Ad Lib detection routine used by some games is reported not to work
Note 4: There is one report of the Plaid Bib (the ancestor to this card) behaving erratically in this model of PS/2. However I have not observed any issues with the Snark Barker MCA.
Note 5: Machine has LAN Adapter/A installed.
If you build the card and try it out, please let me know how it went. Be sure to give me the full part number of your computer along with any installed options (3rd-party planar, memory cards, etc). If you're located in Silicon Valley, you could also loan me (or even give me!) a computer not on this list and I will test for compatibility myself.
Configuration: No cards installed.
The joystick port conflicts with the SCSI host that is built into the planar and must be disabled.
The configuration tested included
- 8MB RAM (on the planar)
- ESDI hard drive with DOS 6.22 and Windows 3.11 installed
- Buslogic BT640A SCSI card
- IBM XGA-2 video card
Although not fully understood, this configuration experiences what appear to be IRQ conflicts. The Micro Channel bus allows IRQ sharing, but not all software supports this correctly, so it may be related to that. "Doom" only works when using IRQ2. A workaround is to replace the default DOS4GW DOS extender with the DOS32A extender; this allows IRQ5 and IRQ7 to work correctly.
The Windows Sound Blaster driver crashes unless it is replaced with the driver recommended by Creative Labs for the SB Pro MCV. "VDMAD.386" is in the SB Pro MCV driver pack.
Some PS/2 machines experience a "Bus timeout error" when running Windows
3.1 in enhanced mode. If you have this problem, Copy VDMAD.386 to your
WINDOWS\SYSTEM sub-directory and change the following line under the [386Enh]
section in your SYSTEM.INI file.
[386Enh]
;change this line
DEVICE=*VDMAD
;to this line
DEVICE=VDMAD.386
You can also fix it by first starting Windows in standard mode, win /s, exit, and then start Windows in enhanced mode win as you normally would.
The joystick seems to conflict with something else and the setup program turns it off.
Getting Doom to run is slightly tricky and requires a hack. It only worked when IRQ was set to 5 and DOS4GW was replaced with DOS32A, but this version doesn't properly initialize the sound card. The hack is this:
- Make a copy of DOOM.EXE:
copy doom.exe doom_p.exe - Apply the DOS32A patch:
sb /r doom_p.exe - Run the original first:
doomand let it crash back to the DOS prompt. - Run the patched executable:
doom_p
You will need the ADF (adapter description file) in order to set up the Snark Barker MCA on your Micro Channel computer.
Place the file on a 3 1/2" floppy disk. After you install the card and boot the computer, it will detect that a new card has been installed and prompt you to insert the reference disk. Do this and follow the prompts. When the setup utility asks you to insert the option disk, use the one that contains the ADF file. After the setup utility configures the card, it will prompt you to reboot the machine.
Plug your line-level audio amplifier input into the card's 3mm audio jack nearest the joystick port. The other audio jack above that one is for the microphone input.
Once that's finished, try out the Snark Barker MCA with your favorite game!
Hoo boy, this one is a doozie. Someone once told me
At Creative Labs tech support we would always get a sinking feeling whenever someone said they had a SoundBlaster MCA. Guaranteed at least a 45 minute call. Weekly average call time blown straight to hell.
Keep in mind that Micro Channel systems can be difficult to troubleshoot due to the large number of possible configurations and the varied implementations of the bus. Not all games will even work on some PS/2 systems even without a sound card!
Here are a few things to try out first before you starting really digging in:
- Is the CPLD soldered in correctly, with no solder bridges? Did you program it?
- Are there potentially bad or fake chips? Some users have reported issues with fake NE555s or fake 74ALS245 chips.
- Did you program and install the 8051 (DSP)?
- If the BIOS detects and installs the card, but you have issues with the audio, try removing all the expansion cards except for the Snark Barker
- Try running SBDIAG
Computer will not boot at all, Computer boots but does not detect the card
Suspect the CPLD. Check for bad solder joints. Is pin 1 oriented correctly? Compare it with the photo.
Did you use something other than a 74HCT245 or 74ALS245 for U2? Slower logic families can "crash the bus" and prevent the system from booting.
Joystick doesn't function
Is the joystick enabled? Run the setup program and navigate to "Change Configuration" and see if the joystick is on or off. The setup program may have turned it off due to a conflict with another card (Ethernet cards often like to use the joystick port location).
No digitized sound. Digitized sounds play but are cut off
It is possible that you have an IRQ conflict. Micro Channel allows for IRQ sharing and not all games support this correctly. Try changing the IRQ using the setup program's "Change Configuration" menu and see if that helps.
Since games implement Sound Blaster support in different ways, some programs may work and others may not!
The card causes random errors with the hard disk, or other cards
Do you have a legitimate 74ALS245, or is it fake? A user reported that swapping this part out with a legitimate one solved the problem for him.
If you have an HP logic analyzer, like a 1670 or 16700 series, you can connect three cables to the Snark Barker MCA using standard HP 01650-63203 termination adapters. The pin assignments are as follows:
| Pin | J2 | J4 | J5 |
|---|---|---|---|
| CLK | CMD | ADL | PREEMPT |
| D0 | BUSRESET | A0 | DS16RTN |
| D1 | M_IO | A1 | CHRDYRTN |
| D2 | S0_WRITE | A2 | MADE24 |
| D3 | S1_READ | A3 | CD_DS16 |
| D4 | CD_SETUP | A4 | TC |
| D5 | REFRESH | A5 | ARB/GNT |
| D6 | CD_SFDBK | A6 | CHCK |
| D7 | CD_CHRDY | A7 | IRQ7 |
| D8 | DB0 | A8 | IRQ5 |
| D9 | DB1 | A9 | IRQ3 |
| D10 | DB2 | A10 | IRQ2 |
| D11 | DB3 | A11 | ARB3 |
| D12 | DB4 | A12 | ARB2 |
| D13 | DB5 | A13 | ARB1 |
| D14 | DB6 | A14 | ARB0 |
| D15 | DB7 | A15 | BURST |
Or, you can load this configuration file onto your HP analyzer and save a bunch of manual data entry. J2 goes to pod 1, J4 goes to pod 2, and J5 goes to pod 3.
An additional debug header, J6, brings out a few additional signals:
| Pin | J6 |
|---|---|
| 1 | DBG1 (CPLD unassigned) |
| 2 | CLK_14M318 (MCA bus clock) |
| 3 | DBG3 (CPLD unassigned) |
| 4 | DBG4 (CPLD unassigned) |
| 5 | DBG5 (CPLD unassigned) |
| 6 | DBG6 (CPLD unassigned) |
| 7 | DBG7 (CPLD unassigned) |
| 8 | SBHE (MCA bus signal) |
| 9 | GND |
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