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CPS-3 converts

CPS-3 does not convert "by reprogramming EPROMs": the game is encrypted, stored on CD, then written to flash SIMMs on first boot by the motherboard, under the control of a security cartridge (SH-2 + keys in battery-backed SRAM). Converting = right SIMMs + right cartridge/BIOS pair + the game to flash. The modern route is the Darksoft BIOS (no-CD, no-battery).

Field Value
Platform Capcom CPS-3
Type flashing the SIMMs + handling cartridge/BIOS/keys
Difficulty 🟠 (TSOP48 flashing, possibly cartridge re-BIOS)
Suicide? Yes, severe — keys in battery-backed SRAM in the cartridge

How a CPS-3 boots (understand this first)

  1. The security cartridge holds a custom SH-2 (on-the-fly decryption), the startup BIOS, and the game decryption keys in battery-backed SRAM.
  2. On first boot, the motherboard copies the CD data to the flash SIMMs (a long operation).
  3. Then the game runs from the SIMMs; the CD is no longer read each time.

The suicide

Dead battery = keys wiped = mute board (frozen screen). Capcom no longer repairs these. Every conversion/preservation revolves around this point.

The SIMM bank: 7 slots

The motherboard has 7 SIMM slots. Three capacities (TSOP48 flash, not RAM):

SIMM density Flash chips
32 Mbit 2 chips
64 Mbit 4 chips
128 Mbit 8 chips

Per-game SIMM configuration (essential to convert)

Game S1 S2 S3 S4 S5 S6
Warzard / Red Earth 64M 128M 128M 32M or 128M — —
SFIII: New Generation 64M 128M 128M 32M or 128M — —
JoJo's Venture 64M 64M 128M 128M 32M or 128M —
JoJo's Bizarre Adventure 64M 64M 128M 128M 128M —
SFIII: 2nd Impact 64M 64M 128M 128M 128M —
SFIII: 3rd Strike 64M 64M 128M 128M 128M 128M

→ To convert to a bigger game (e.g. 3rd Strike) you need the right number of SIMMs at the right density; hence the value of repro SIMMs (Darksoft) when you're short on capacity.

The cartridge & the BIOS

The cartridge carries the BIOS in a Fujitsu 29F400 (TSOP48) flash — that's the IC to flash, located next to the big SH-2 (marked "D"). Three cases:

  • Original cartridge of the target game (live battery): it already has the game's BIOS + keys → you "just" flash the SIMMs with that game.
  • Phoenix / no-battery BIOS: flash the 29F400 with a patched BIOS that no longer needs a battery or key → the cartridge boots whatever game is loaded in the SIMMs.
  • Dead (suicided) cartridge: re-flashing the 29F400 is mandatory (pull/flash on a programmer/resolder) — for boards that are already dead.

Flashing the 29F400 BIOS

Two ways: in-circuit (suitable hardware), or remove the 29F400 → flash on a TSOP48 programmer → resolder. TSOP48 is fine-pitch → hot air + precision. Only remove the chip if the cartridge is already dead.

The CD drive (to flash the SIMMs the original way)

CPS-3 loads the game from a SCSI CD-ROM drive:

  • Original models Panasonic CR-504 / CR-505; known compatibles Toshiba XM-3701B, NEC CD-3010A.
  • SCSI ID = 1, parity enabled, termination enabled.

The original way: insert the game CD and the board writes the SIMMs at boot (~40 min for a big game). With Darksoft, no CD needed.

The Darksoft BIOS makes the cartridge universal:

  • No-battery: no battery, no suicide.
  • No-CD: games are flashed to SIMMs and run natively (no key loaded) — the drive is no longer needed.
  • Multi: a single CD (or dump) with all games (~80–100 MB each) is used to flash; you then pick the game to load.

Installation (summary):

  1. Get a cartridge (ideally already no-battery or to be converted) and flash the Darksoft BIOS into the 29F400.
  2. Have the right SIMM set (capacities per game / Darksoft repro).
  3. Flash the SIMMs with the wanted game (via the Darksoft CD / kit procedure).
  4. Boot: the board loads the game without battery or drive.

Keep a live original cartridge

Even when moving to Darksoft, keeping a non-suicided original cartridge (fresh battery) has preservation value — the original keys remain useful.

"Standard SH-2" variant

You can replace the custom SH-2 with a standard SH-2 (removes the encryption requirement), at the cost of a different BIOS. Heavier approach, mostly useful for a cartridge whose custom SH-2 is dead.

Before / after

  • Cart+CD convert: the motherboard runs another game (after SIMM reflash).
  • Darksoft: switch between all games, no battery or laser, fast boot.

Hardware / where to read more

Open-hardware SIMM archived here

CPS3 NOS (NOR Open SIMM), an open-source alternative to the original SIMMs — KiCad sources + gerbers/BOM to fabricate: cps3-nos.tar.gz · README — upstream: https://github.com/herzmx/cps3-nos. (Illustration media stripped to keep it light.) We host no ROMs, BIOS, or keys.

Sources & attribution

Review & corrections

How this space is used

Spotted a wrong value, an outdated procedure, a chip reference that does not match your board? Say so here, with what you observed (model, board revision, serial number, measurement). Every report is cross-checked against a source before anything changes — an unverifiable correction is published as “reported by …, not cross-checked” rather than silently applied.

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