emulator: FCEUmm
type: libretro
source: "https://github.com/libretro/libretro-fceumm"
profiled_date: "2026-03-18"
core_version: "SVN"
display_name: "Nintendo - NES / Famicom (FCEUmm)"
systems: [nintendo-nes, nintendo-fds]

notes: |
  FCEUmm (FCE Ultra mappers modified) is a NES/Famicom emulator.
  NES cartridge games need no BIOS. Famicom Disk System games require
  the FDS BIOS ROM (disksys.rom, 8 KB) loaded from the system directory.
  Game Genie emulation is an optional core feature (disabled by default)
  that requires gamegenie.nes in the system directory.
  An optional external palette file (nes.pal, 192 bytes, 64 RGB triplets)
  can override the built-in NES palette when the core option is set to Custom.
  NstDatabase.xml is NOT used by FCEUmm (that is Nestopia's database).

  File path construction: src/general.c FCEU_MakeFName() joins the
  system directory (RETRO_ENVIRONMENT_GET_SYSTEM_DIRECTORY) with each
  filename directly - no subdirectories.

files:
  # --- Famicom Disk System BIOS (required for FDS games) ---
  - name: "disksys.rom"
    system: nintendo-fds
    description: "FDS BIOS ROM"
    required: true
    size: 8192
    md5: "ca30b50f880eb660a320674ed365ef7a"
    sha1: "57fe1bdee955bb48d357e463ccbf129496930b62"
    source_ref: "src/fds.c:636-667 (FDSLoad), src/general.c:64-66 (FCEUMKF_FDSROM)"
    notes: "Loaded at 0xE000, mapped as 8 KB PRG bank 0. Load fails with error if missing or short read."

  # --- Game Genie ROM (optional, core option fceumm_game_genie) ---
  - name: "gamegenie.nes"
    system: nintendo-nes
    description: "Game Genie add-on cartridge ROM"
    required: false
    size: 24592
    md5: "7f98d77d7a094ad7d069b74bd553ec98"
    sha1: "f430a0d752a9fa0c7032db8131f9090d18f71779"
    source_ref: "src/cart.c:351-389 (OpenGenie), src/general.c:60-62 (FCEUMKF_GGROM)"
    notes: "iNES format ROM (4 KB PRG + 256 bytes CHR). Core option disabled by default. Does not apply to FDS or arcade content."

  # --- Custom palette (optional, core option fceumm_palette) ---
  - name: "nes.pal"
    system: nintendo-nes
    description: "External NES color palette"
    required: false
    size: 192
    md5: "aaf3666e4ed478e2964b46d6a7aa27ad"
    sha1: "37027d92e1015b82a7dc5c43e9f1649a961577ab"
    source_ref: "src/general.c:68-70 (FCEUMKF_PALETTE), src/drivers/libretro/libretro.c:1791"
    notes: "64 RGB triplets (64 x 3 bytes). Only loaded when palette core option is set to Custom. Multiple valid palettes exist."