FCEUmm

FCEUmm emulates Nintendo NES and Nintendo Famicom Disk System. It reads 3 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/libretro/libretro-fceumm
Upstream	https://sourceforge.net/projects/fceumm/
Version	none stated in the source
Revision	libretro/libretro-fceumm@ac0d00a7fc01
Profiled	2026-03-23
Profile	YAML, JSON
Cores	fceumm
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://abdess.github.io/retrobios/i.ps1))) --emulator fceumm

macOS

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

Terminal

curl -fsSL https://abdess.github.io/retrobios/i | sh -s -- --emulator fceumm

Linux

Open a terminal. Paste the line. Press Enter.

Terminal

curl -fsSL https://abdess.github.io/retrobios/i | sh -s -- --emulator fceumm

Steam Deck

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

Terminal

curl -fsSL https://abdess.github.io/retrobios/i | sh -s -- --emulator fceumm

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://abdess.github.io/retrobios/i | sh -s -- --emulator fceumm

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://abdess.github.io/retrobios/i | sh -s -- --emulator fceumm

Technical 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

3 files: 1 required, 2 optional.

In this collection: 3 in repo and 0 missing.

Required

disksys.rom required for Nintendo Famicom Disk System in repo

FDS BIOS ROM

• System: Nintendo Famicom Disk System
• Loaded at 0xE000, mapped as 8 KB PRG bank 0. Load fails if missing or short read.

• Size: 8.0 KB
• Collection copy: bios/Arcade/FBNeo/fdsbios.nes
• Platforms: disksys.rom: Batocera, EmuDeck, KNULLI, Lakka, RetroArch, RetroBat, RetroPie. bios/disksys.rom: AmberELEC, EmuELEC, RetroDECK. fds/disksys.rom: Recalbox, RomM. FDS_disksys-nintendo.rom: BizHawk. NES/boot0.rom: MiSTer FPGA

Validation and source

• Validation: size
• Source: src/fds.c:680-715, src/general.c:65-67

Optional

gamegenie.nes optional in repo

Game Genie add-on cartridge ROM

• System: Nintendo NES
• iNES format ROM (4 KB PRG + 256 bytes CHR). Core option disabled by default. Only applies to cartridge games.

• Collection copy: bios/Nintendo/NES/gamegenie.nes
• Platforms: gamegenie.nes: Lakka, RetroArch, RetroPie

Source

• Source: src/cart.c:401-455, src/general.c:61-63

nes.pal optional in repo

External NES color palette

• System: Nintendo NES
• RGB triplets (64 standard or 512 with de-emphasis). Only loaded when palette core option is set to Custom.

• Collection copy: bios/Nintendo/NES/nes.pal

Source

• Source: src/palette.c:170-200, src/general.c:69-71, src/drivers/libretro/libretro.c:1992-2001

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 4 November 2026.