INES Mapper 023
iNES Mapper 023 is used to represent the VRC4e (PCB 352396) and VRC4f (unlicensed games) variants of the Konami VRC4 mapper and the VRC2b (PCBs 350603, 350636, 350926, and 351179) variant of the Konami VRC2 mapper.
For details see the following:
Note that the VRC4e variant uses different address lines to select registers than the VRC2b and VRC4f variants. Your emulator implementation must either combine address lines (like FCEUX; bitwise OR is good enough), use checksums, or NES 2.0 submappers.