NES 2.0 Mapper 458

NES 2.0 Mapper 458 denotes the MMC3-based K-3102 (submapper 0) and GN-23 (submapper 1) multicart PCBs. The MMC3 is only used for CHR banking and mirroring, while all PRG banking is controlled by an extra register, similar to NES 2.0 Mapper 259.

Extra Register ($6000-$7FFF, write)

A~[011. .... d.DM PPPP]
             | || ++++- PRG A17..A14
             | || +---- 0: NROM-128, 1: NROM-256 (submapper 1)
             | |+------ 0: NROM-128, 1: NROM-256 (submapper 0)
             | +------- 0: Normal, 1: Replace CPU A4..0 with solder pad value (submapper 0)
             +--------- 0: Normal, 1: Replace CPU A4..0 with solder pad value (submapper 1)
Value on reset: $00

Notes

• WRAM must be enabled in $A001.7 before writing to the extra register.