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