emulator: RustyNES
type: libretro
core_classification: official_port
source: "https://github.com/doublegate/RustyNES"
upstream: "https://github.com/doublegate/RustyNES"
profiled_date: "2026-09-03"
source_commit: "4e77905e045c0e971b53c5abee8d0a07a4b1bfdb"
core_version: "2.6.12"
display_name: "Nintendo - NES / Famicom (RustyNES)"
cores:
  - rustynes
systems:
  - nintendo-nes
  - nintendo-fds

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.

files:
  - name: "disksys.rom"
    system: nintendo-fds
    description: "Famicom Disk System BIOS"
    required: true
    size: 8192
    validation: [size]
    source_ref: "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"
    note: "Read only when the content extension is .fds. Any other size fails the load."