Category:Mappers with battery-backed CHR-RAM

Very few boards use a battery to retain the content of CHR-RAM. The purpose of doing so is presumably that if a game already uses CHR-RAM for other reasons and only has a few bytes of save data to retain, storing these bytes in the same CHR-RAM chip (and sacrificing available tile numbers in the process) and connecting a battery to it is more economical than adding a separate WRAM chip.

Nintendo's early MMC1 data sheet mentions an "SLROM" board with 8 KiB of battery-backed CHR-RAM. The actual SLROM board that went into production uses CHR-ROM and no PRG-RAM or CHR-RAM at all.