MiSTer FPGA just got its first CPS3 core release

Jotego has released the Capcom Play System 3 core to his Patreon members. The beta brings Street Fighter III: New Generation and Red Earth to the MiSTer FPGA. It is live right now for subscribers, with a full public release planned for the near future.

Capcom introduced the CP System III in 1996 as the successor to its wildly successful CPS2 hardware. It ended up being the company's final proprietary arcade board before they shifted to Sega's Naomi platform. The hardware is famous for pushing 2D pixel art to its absolute limits. It used a CD-ROM drive and security cartridges to load massive amounts of animation data into memory.

The original arcade boards are notoriously fragile today. Capcom used a custom decryption setup with a battery-backed security cartridge. When the battery inevitably dies, the decryption keys vanish, and the game stops working entirely. Getting this specific architecture running accurately on FPGA is a major milestone for arcade preservation. The entire CPS3 library only consists of six games, but they are some of the most visually impressive 2D fighters ever made.

Fitting it into standard RAM

The core took about three months of active development. The most complex hurdle was designing an architecture fast enough to work on standard MiSTer SDRAM without requiring extra hardware modules. Jotego spent two solid weeks debugging a stubborn FPGA compiler issue just to get the project over the finish line.

Jotego mentioned he had never actually played Street Fighter III before building this core. The fluid animation and vibrant colors quickly won him over.

Right now, the beta only supports games that fit within a 64MB SDRAM footprint. The initial release relies entirely on the "No CD" arcade ROM sets. There are no plans to support the original CD images since the game data is identical.

Don't ask for a Pocket version

Anyone hoping to play Red Earth on the bus is out of luck. The CPS3 architecture is simply too large to fit inside the Analogue Pocket. It does not matter if the core can technically be optimized further. The hardware ceiling is too low, so a Pocket port is completely off the table. A version for the SiDi128 FPGA board is planned, but it is not ready for this week's release.

The core is highly playable today, but it is still a beta. There are several known visual glitches, including solid color squares appearing randomly, artifacts in the text, and a horizontal offset on the score graphics. The full-screen zoom effect is currently missing, and pausing the game halts the music. DMA timing also needs verification against real arcade hardware.

Jotego plans to knock out these bugs and release new supported games every week until the entire CPS3 catalog is playable.

In unrelated but welcome news, today's update files also include a fix for the Gradius III core. The sound issues are finally resolved. The bug where your ship randomly dies is still present, which feels like a very authentic arcade experience anyway.