G-MMC1 (Game Boy mapper)

G-MMC1 (also known as MB1M?) is an official Game Boy mapper chip by Nintendo. It is used for GB Memory Cartridge functionality.

The GB Memory Cartridge was a special Game Pak for the Japanese Nintendo Power cart writing service (the Nintendo Power service also supported Super Nintendo Entertainment System) which could hold multiple games at once (individual games both from Nintendo and third-party IP) at Lawson stores in Japan via a Loppi Nintendo Power copier device) in a multi-loader menu and news feed, at cheaper than the usual price. The rewriting service is now discontinued, but after the games have been written they can be played an unlimited number of times.

These cartridges served as multi-carts for a limited selection of games such as Super Mario Land, Tetris and a few (then) unique ones such as Balloon Fight GB.

Another licensed Game Boy mapper 'multi-game' chip was the MMM01) for a select few Game Boy or Game Boy Color games but those games were not developed or published by Nintendo. The games within the MMM01 games were also not expected to be rewritten.