NES 2.0 Mapper 294

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NES 2.0 Mapper 294 is used for the Super Cool Boy 4-in-1 (CB-4035) multicart. It uses an MMC3 clone with a WRAM replaced by an outer bank register.


Outer Bank Register ($6001)

Mask: $E003

7654 3210
.... .SOO
      +++- Select outer 128 KiB bank (bit 0 ignored in 256 KiB mode)
      +--- Select outer PRG/CHR bank size
           0: 256 KiB
           1: 128 KiB

Unknown registers ($6000, $6002, $6003)

The multicart menu writes the same values ($00 to $6000 when the menu is shown, $FF to $6002 and $00 to $6000 when a game is selected) for every game.

MMC3-compatible registers ($8000-$FFFF)

Mask: probably $E001
$8000, $8001, $A000, $A001, $C000, $C001, $E000, $E001: As normal MMC3.


  • Because the outer bank registers are connected to where WRAM would normally be, WRAM needs to be enabled via bit 7 of MMC3 register $A001 before accessing the outer bank registers.