FCEUmm Mod

FCEUmm Mod emulates Nintendo NES and Nintendo Famicom Disk System. It reads 2 files, 1 of them required: without a required file it does not start games. A required file is needed only by the machines that use it. Each file below cites the line of source code that reads it.

About this profile

Detail	Value
Type	libretro
Classification	Community fork
Source	https://github.com/Tippek/libretro-fceumm-mod
Upstream	https://github.com/libretro/libretro-fceumm
Version	SVN
Revision	Tippek/libretro-fceumm-mod@f0ea52190427
Profiled	2026-10-22
Profile	YAML, JSON
Cores	fceumm_mod
Systems	Nintendo NES, Nintendo Famicom Disk System

Install this emulator's files

The installer finds your setup and its BIOS folder, then downloads only the files this emulator reads there and checks each one.

Windows

Open the Start menu. Type PowerShell and open it. Paste the line. Press Enter.

PowerShell

&([scriptblock]::Create((irm https://raw.githubusercontent.com/Abdess/retrobios/main/install.ps1))) --emulator fceumm_mod

macOS

Open Terminal, in Applications, then Utilities. Paste the line. Press Return.

Terminal

curl -fsSL https://raw.githubusercontent.com/Abdess/retrobios/main/install.sh | sh -s -- --emulator fceumm_mod

Linux

Open a terminal. Paste the line. Press Enter.

Terminal

curl -fsSL https://raw.githubusercontent.com/Abdess/retrobios/main/install.sh | sh -s -- --emulator fceumm_mod

Steam Deck

Switch to Desktop Mode. Open Konsole. Paste with Ctrl+Shift+V. Press Enter.

Terminal

curl -fsSL https://raw.githubusercontent.com/Abdess/retrobios/main/install.sh | sh -s -- --emulator fceumm_mod

Android (Termux)

Install Termux, a terminal app. Run pkg install python and termux-setup-storage once. Then paste the line. Press Enter.

Terminal

curl -fsSL https://raw.githubusercontent.com/Abdess/retrobios/main/install.sh | sh -s -- --emulator fceumm_mod

On the device

Open a terminal on the device. Or connect from a computer with SSH, a terminal over the network. Paste the line. Press Enter.

Terminal

curl -fsSL https://raw.githubusercontent.com/Abdess/retrobios/main/install.sh | sh -s -- --emulator fceumm_mod

Technical notes

libretro-fceumm with the hardware extensions of fceux-mod (extra RAM, sprites, palettes and mappers). The libretro driver hands the system directory to FCEUI_SetBaseDirectory (src/drivers/libretro/libretro.c:2983-2984) and FCEU_MakeFName joins each name to it directly (src/general.c:70-97).

The Game Genie image is named gg.rom here (src/general.c:77-79), but FCEU_OpenGenie runs only when FSettings.GameGenie is set (src/fceu.c:283-285) and nothing in the libretro driver calls FCEUI_SetGameGenie (src/fceu.c:551-554), so the file is never opened.

Files

2 files: 1 required, 1 optional.

In this collection: 2 in repo and 0 missing.

Required

disksys.rom required for Nintendo Famicom Disk System in repo

FDS BIOS ROM

• System: Nintendo Famicom Disk System

• Size: 8.0 KB
• Validation: size
• Source: src/fds.c:612-650, src/general.c:80-82
• Collection copy: bios/Arcade/FBNeo/fdsbios.nes
• Platforms: AmberELEC: bios/disksys.rom, Batocera: disksys.rom, BizHawk: FDS_disksys-nintendo.rom, EmuDeck: disksys.rom, EmuELEC: bios/disksys.rom, KNULLI: disksys.rom, Lakka: disksys.rom, MiSTer FPGA: NES/boot0.rom, Recalbox: fds/disksys.rom, RetroArch: disksys.rom, RetroBat: disksys.rom, RetroDECK: bios/disksys.rom, RetroPie: disksys.rom, RomM: fds/disksys.rom

• Read as one 8 KB PRG bank. A missing file or a short read fails the FDS load.

Optional

nes.pal optional in repo

External NES color palette

• System: Nintendo NES

• Source: src/palette.c:191-212, src/fceu.c:289-290, src/drivers/libretro/libretro.c:1674-1682, src/drivers/libretro/libretro.c:3013-3017
• Collection copy: bios/Nintendo/NES/nes.pal

• Read at every game load when present, 768 bytes of RGB triplets. Applied when the fceumm_palette option is custom.

Next steps

• Get your files, for the setup you play on
• Every system, and the files each one needs
• When a game does not start

Data as of 24 October 2026.