romdev-core-bsnes

The bsnes SNES libretro core, compiled to WebAssembly for romdev.

romdev's default SNES core is snes9x. bsnes is here as the accuracy reference for the SNES coprocessors that run firmware, which snes9x only approximates: the ST010/ST011 (a NEC uPD96050) and the ST018 (an ARM). bsnes runs their firmware; put st011.rom / st018.rom (the program ROM followed by the data ROM, as the chips are dumped) in the core's system directory. romdev loads it with loadMedia({platform:'snes', core:'bsnes'}) or as the reference of frame({op:'verifyRecompile', referenceCore:'bsnes'}).

The build differs from upstream in these ways, all in romdev's patches and build script:

• libco gets a WebAssembly backend: bsnes runs every chip as a cothread, and the cothreads switch with binaryen's Asyncify inside the module;
• the libretro target serves memory regions with romdev's SNES region ids (system_ram, video_ram, save_ram, snes_oam, snes_cgram, snes_aram, snes_chipstate) and finds coprocessor firmware in the system directory;
• the reference defaults are deterministic and accurate: no entropy, the accurate PPU and DSP, no HLE preference;
• no Nintendo boot ROM or chip data: the SPC700 boot ROM is romdev's own clean-room one (MIT, scripts/spc700-ipl/), and the DSP-1 data ROM, the ST010 tables, the Cx4 data ROM and the Super Game Boy boot ROMs upstream embeds are emptied. A DSP-1, DSP-2, DSP-3, DSP-4, ST010 or ST011 cart needs the chip's firmware in the system directory (e.g. dsp1b.rom, st010.rom, the program ROM then the data ROM) and is refused with the file named without it (DSP-2 and DSP-4 fall back to bsnes's high-level emulation); a Cx4 cart runs bsnes's high-level emulation unless cx4.data.rom is there; the Super Game Boy needs sgb_boot.bin / sgb2_boot.bin.

License: GPL-3.0-only (bsnes; libco and nall are ISC). See NOTICE. Not intended for standalone use; loaded by romdev's core registry. This core is a separate reference: none of its code is compiled into romdev's snes9x core or into recompiled carts (their firmware coprocessors come from ares, ISC).

No coprocessor firmware ships in this package: supply your own dumps, for example with loadMedia({platform:'snes', core:'bsnes', firmware}), which copies the file into the system directory before the ROM loads.

Built by: packages/romdevtools/scripts/build-bsnes.sh with bsnes-romdev.patch and bsnes-romdev-firmware.patch (plus patches/bsnes/ and patches/libco-wasm/). See BUILD_MAP.md for the recipe-to-package map.