Many EPROM, like the 27C801, have less address lines than the SNES hi/lo roms have. The highest address line I have seen was an A21 on some TSOP 40's. Are A22 and A23 not used very often, or is there some form of bypass around these addresses?
More address lines just means it's a bigger ROM. A 32Mbit ROM will have address lines 0-22, 16Mbit 0-21, 8Mbit 0-20, etc. Each additional address line doubles the size.
i have been looking at this 32 mbit 40 pin tsop, and it only has address lines up to 21 not 22. is this normal?
http://www.buyicnow.com/files/datasheet/EEPROM/1070.pdf
also, the 27c801 has 19 addresses not 20, so does it go 32 mbit 0-21, 16 mbit 0-20, 8 mbit 0-19?