Mapper
También conocido como: memory mapper , mmc , mapper chip , mappers
A mapper (or "memory mapper") is custom hardware on a game cartridge that bank-switches more ROM and RAM into the console's narrow address space than a flat layout could fit. NES games used over a hundred different mapper chips (MMC1, MMC3, etc.) and each behaves differently — bank switching, scanline IRQs, mirroring control, expansion audio. Emulators implement each known mapper as a software module; running an obscure cartridge is sometimes blocked by the mapper not being implemented yet, not the CPU emulation.