snes-st010

A free, clean-room implementation of the ST010, the Seta coprocessor (an NEC uPD96050) in F1 ROC II: Race of Champions, under the GPL. It answers the chip's commands with the same results as the original, so emulators can run the game without the original chip's program, which is the chip maker's code.

F1 ROC II's reads of the chip, from power-on into a race: 99.9997% the same (25 of 7.8 million differ, from two tables of the chip's whose odd entries aren't copied). The commands: docs/commands.md; how exact: docs/exactness.md.

#include "st010/St010.h"

st010::St010 chip;
chip.writeRam(address, byte);   // the chip's 4 KiB of RAM as the SNES maps it; setting bit 7 of
uint8_t b = chip.readRam(address);  // 021h runs the command in 020h at once
uint8_t* save = chip.ram();     // battery-backed: keep it with the game's save
auto state = chip.saveState();  // for save states
chip.loadState(state.data(), state.size());

cmake -S . -B build && cmake --build build && (cd build && ctest)
build/st010_check RECORDING...   # replay traffic recorded with the original chip

Made by StackBlender for Super Apollo, an emulator that plays SNES games fast with their music at normal speed. Its other chips are published the same way: snes-dsp1, snes-dsp2, snes-cx4, snes-dsp4.

How it is made

Clean room: written from the public list of the chip's commands (their names) and from measuring what the original does, never from the original program's bytes or a disassembly of it, which nobody on this project reads. It is checked against the original running in the ares emulator, answer for answer; the tests take the original from the emulator at run time, and it is never in this repository. The rules: docs/clean-room.md.

License

GNU General Public License, version 3 or (at your option) any later version; see LICENSE. For other terms, contact StackBlender.