emulator: FCEUmm
type: libretro
core_classification: community_fork
source: "https://github.com/libretro/libretro-fceumm"
upstream: "https://sourceforge.net/projects/fceumm/"
profiled_date: "2026-03-23"
core_version: "SVN"
display_name: "Nintendo - NES / Famicom (FCEUmm)"
cores:
  - fceumm
systems: [nintendo-nes, nintendo-fds]

notes: |
  FCEUmm (FCE Ultra mappers modified) is a NES/Famicom emulator forked from
  FCEU Ultra by CaH4e3. FDS games require the FDS BIOS ROM (disksys.rom).
  Game Genie emulation requires gamegenie.nes when the core option is enabled.
  An external palette file (nes.pal) overrides the built-in palette when the
  core option is set to Custom.

  File path construction: src/general.c FCEU_MakeFName() joins the 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
    validation: [size]
    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 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
    source_ref: "src/cart.c:344-398 (FCEU_OpenGenie), src/general.c:60-62 (FCEUMKF_GGROM)"
    notes: "iNES format ROM (4 KB PRG + 256 bytes CHR). Core option disabled by default. Only applies to cartridge games."

  # --- Custom palette (optional, core option fceumm_palette) ---
  - name: "nes.pal"
    system: nintendo-nes
    description: "External NES color palette"
    required: false
    source_ref: "src/palette.c:170-200 (FCEU_LoadGamePalette), src/general.c:68-70 (FCEUMKF_PALETTE), src/drivers/libretro/libretro.c:1789-1798"
    notes: "RGB triplets (64 standard or 512 with de-emphasis). Only loaded when palette core option is set to Custom."