Expand description
The DSP-1 board — the µPD77C25 wired into a LoROM/HiROM cartridge.
DSP-1 (NEC µPD77C25, the uPD7725 revision of the shared engine) is the Mode-7 3D-math
coprocessor in 15+ titles (Super Mario Kart, Pilotwings, Super Bases Loaded 2). It exposes
exactly two memory-mapped ports — the data register (DR) and the status register (SR) — at a
board-dependent bus window. There is no canonical per-game window table; this board picks the
de-facto window from the map mode + ROM size, the heuristic snes9x/bsnes use when no cartridge
database is present, which coincides with every ares DSP-1 board definition:
| Map mode / size | DSP window (banks : addr) | DR / SR split |
|---|---|---|
| HiROM | $00–$1F,$80–$9F : $6000–$7FFF | DR $6xxx, SR $7xxx |
| LoROM, ROM ≤ 1 MiB | $30–$3F,$B0–$BF : $8000–$FFFF | DR $8–$Bxxx, SR $C–$F |
| LoROM, ROM > 1 MiB | $60–$6F,$E0–$EF : $0000–$7FFF | DR $0–$3xxx, SR $4–$7 |
ROM and SRAM decode is delegated to the wrapped base board; only the DSP window is
intercepted. The board is functional only once the user supplies the dsp1.rom / dsp1b.rom
firmware dump (docs/adr/0003 — a chip-ROM-dump coprocessor is never silently degraded).
Structs§
- Dsp1
Board - A LoROM/HiROM cartridge carrying a DSP-1 (µPD77C25).