User:Zzo38/Mapper B

This mapper is defined by tepples as "Mapper 670".

CPU address space:

• $8000-$9FFF: Switchable bank 0
• $A000-$BFFF: Switchable bank 1
• $C000-$DFFF: Switchable bank 2
• $E000-$EFFF: Switchable bank 3
• $F000-$FFFF: Fixed to last bank

Banks are switched by writing the 8K bank number into the low four bits of registers in the same address space where the banks are at. There is no bus conflicts.

Sometimes there may be PRG RAM at $6000-$7FFF. Usually there is 8K CHR RAM, although there might be 8K CHR ROM.