Hardware

MMC3

The NES power expander

Nintendo's MMC3 mapper chip enabled larger, more sophisticated NES games through bank switching, scanline counting, and expanded capabilities.

NES mappernesenhancement 1988–present

Overview

The NES’s base hardware had limitations that mapper chips overcame. The MMC3 (Memory Management Controller 3) was Nintendo’s most widely used advanced mapper, enabling bank switching for larger ROMs, scanline IRQs for split-screen effects, and additional RAM. Games like Super Mario Bros. 3 and Kirby’s Adventure used MMC3 to exceed what the base NES could achieve.

Fast facts

  • Manufacturer: Nintendo.
  • Purpose: extend NES capabilities.
  • Features: bank switching, scanline counter, extra RAM.
  • PRG ROM: up to 512KB.
  • CHR ROM/RAM: up to 256KB.
  • Notable games: SMB3, Mega Man 3-6, Kirby’s Adventure.

Capabilities

What MMC3 enabled:

  • Bank switching: access larger ROM space.
  • Scanline IRQ: trigger interrupts at specific lines.
  • Split screen: status bars, different scroll regions.
  • More graphics: larger tilesets.

Programming use

MMC3 for developers:

  • Bank registers: select active ROM banks.
  • IRQ counter: load value, count down per scanline.
  • PRG banking: 8KB switchable banks.
  • CHR banking: 1KB or 2KB banks.

See also