The generic designation FxROM refers to cartridge boards made by Nintendo that use the Nintendo MMC4 mapper.
The following FxROM boards are known to exist:
| Board | PRG ROM | PRG RAM | CHR |
|---|---|---|---|
| FJROM | 128 / 256 KB | 8 KB | 16 / 32 / 64 KB ROM |
| FKROM | 128 / 256 KB | 8 KB | 128 KB ROM |
On the FKROM board, battery backup appears to be compulsory unless there is a hidden solder pad below the MM1026 chip.
The FKROM board uses a Mitsumi MM1026 chip dedicated to safe battery backup. It's the only Nintendo board to use a specific chip dedicated to safe battery backup.
Categories: Nintendo licensed mappers