http://www.neogaf.com/forum/showthread.php?t=456554&page=3 のっとマスクROM
XtraROM
NROM (Nitride ROM)
Macronix announces a new nitride-based multiple bits/cell technology - NBit(TM), starting with 2bits/cell solutions.
This trap-charge technology stores two bits of information in each cell which provides double the storage capacity for the same die size in comparison to conventional technologies.
This technology is utilized to provide highly cost-effective NOR Flash and Mask ROM solutions across a wide range of densities.