RustyNES - RetroBIOS¶
Technical notes
RustyNES is a NES and Famicom emulator written in Rust by DoubleGate. The libretro core is the crates/rustynes-libretro crate of the same repository, built from the main branch (crates/rustynes-libretro/Makefile, .gitlab-ci.yml). The crate pulls rustynes-core with default features off, so the HD pack loader is not compiled into the core and nothing else is read from disk.
Cartridge content needs no external file. A .fds disk image goes to Nes::from_disk, which needs the Famicom Disk System BIOS: the core joins disksys.rom to the frontend system directory and reads the whole file (crates/rustynes-libretro/src/lib.rs:921-938). A missing file, or a frontend without a system directory, makes retro_load_game fail with an error. Fds::new rejects a BIOS that is not exactly 8192 bytes (crates/rustynes-mappers/src/fds.rs:1351-1357); no hash is checked. The FDS device maps the BIOS and boots from its reset vector.
The version comes from the workspace Cargo.toml. The .info in libretro-core-info says v2.3.5 and the copy in the repository v2.6.12; the md5 in the .info notes is not enforced by the code.
1 files | 1 required, 0 optional | 1 in repo, 0 missing
disksys.rom required in repo
Famicom Disk System BIOS
- System: nintendo-fds
- Size: 8.0 KB
- Validation: size
- Source:
crates/rustynes-libretro/src/lib.rs:921-945,crates/rustynes-core/src/nes.rs:356-358,crates/rustynes-core/src/bus.rs:1015-1021,crates/rustynes-mappers/src/fds.rs:121,crates/rustynes-mappers/src/fds.rs:1351-1357 - Platforms: batocera, emudeck, lakka, recalbox, retroarch, retrobat, retrodeck, retropie, romm
- Read only when the content extension is .fds. Any other size fails the load.
Generated on 2026-09-14T09:03:10Z