Bringing open, software-defined hardware to the IBM PS/2 Micro Channel bus.
WonderMCA is an open-source expansion-card project for IBM PS/2 machines built around the RP2350 (Raspberry Pi Pico 2). In the spirit of PicoMEM and PicoGUS, it aims to bring modern, software-defined peripherals — sound, memory and I/O — to a platform that has been starved of affordable expansion cards for decades.
Why WonderMCA
Micro Channel machines have always been the awkward cousins of the retro-PC world: powerful for their day, but locked behind a proprietary bus with scarce documentation and almost no modern, open hardware. Working MCA expansion cards are rare and expensive when they appear at all.
WonderMCA exists to change that — a single, reprogrammable card that emulates the peripherals MCA users actually want, built in the open so the community can use, study and extend it.
What it does
- Sound Blaster audio (SBDSP) — full DSP emulation with working DMA on the Micro Channel bus, sharing the proven PicoMEM sound software base. (The hard-won milestone — see the build log.)
- Memory expansion — additional RAM mapped onto the MCA bus.
- I/O paths — flexible, software-defined I/O for emulated devices.
- One reprogrammable card — capabilities grow over time with firmware updates.
The MCA challenge
Micro Channel is not ISA. There is no 8237 DMA controller to lean on, arbitration runs through the CACP, and the timing and signalling are a world apart — all with very little surviving documentation. Getting something as “simple” as Sound Blaster DMA to work meant reverse-engineering the bus behaviour across multiple machines. That journey is documented, warts and all, in the build log.
Compatibility (under test)
WonderMCA targets 286/386-class IBM PS/2 Micro Channel machines. Testing so far spans a range of chassis, including:
| IBM PS/2 model | Status |
|---|---|
| Model 8550 / 8550Z | Tested |
| Model 8555 | Tested |
| Model 8556 / 8557 | Tested |
| Model 8570 (386DX) | Tested |
| Other 286/386 MCA chassis | In progress |
Compatibility is evolving as development continues — check the build log for the latest matrix.
Build log
Follow the full story of WonderMCA, from first idea to first sound:
- Part 1 — The origin
- Part 2 — MEM & I/O path working
- Part 3 — Hunting a ghost: how MADE24 broke /CMD on 386 PS/2
- Part 4 — From silence to TADA: Sound Blaster DMA on MCA
Get involved
WonderMCA is built in the open and powered by the retro community. Want one when it’s ready, or want to follow the build?