Memory management controller. These were
co-processors built into
NES/
Famicom cartriges to do things that the NES could not normally do, such as hold up to a
megabyte of ROM, hold battery-backed
RAM, hold additional
work RAM, produce 360-degree scrolling (not rotating) planes, and cram more colors into smaller areas. There was the
MMC1,
MMC2,
MMC3,
MMC4,
MMC5 and
MMC6. They were built into the game cartrige rather than into a separate hardware upgrade so as to not confuse consumers with multiple formats. Nintendo didn't even mention the MMCs in their marketing. They simply showed the games getting better and better.
The downside of MMCs was that they, and the extra RAM that came with them, kept NES games expensive. Even as ROM prices fell and NES games were more mass produced, NES games continued to sell for $40 to $50 new.
Camerica tried to solve this problem with the
Aladdin Deck Enhancer, which had an MMC-like chip, extra RAM and battery built in, so that the NES owner would only have to buy them once, and then could buy top-quality NES games that cost only $15 to $30. Unfortunately, since the Aladdin was an unlicensed and undermarketed product that came out when the NES was already going out of style, few people used it .
Nintendo revisited integrated enhancer chips in 1993 with the
Super FX, a polygon processor for the Super NES that premiered in
Starfox. This time, Nintendo made a big deal of it in their advertizing, helped by the fact that
Starfox was strikingly different from un-enhanced
Super NES games, compared to MMC NES games which were only subtly different from eachother. But, just like the MMCs, the Super FX raised the price of whatever game it accompanied.