INES Mapper 123

iNES Mapper 123 is used for the 卡聖 (Kǎshèng) H2288 board, an MMC3-clone-bearing board with scrambled register indices, and an NROM-like PRG-ROM register that can override the MMC3 clone's PRG-ROM bank. Its UNIF board name is UNL-H2288. Used by:

• Mortal Kombat 3 (Kǎshèng/Hummer Team, not to be confused with Mortal Kombat 3 from SuperGame)
• Earthworm Jim 2 (Kǎshèng/Shin-Shin Electronics, not to be confused with Earthworm Jim 2 from SuperGame)

Registers

NROM Override Register ($5800)

Mask: $F800

D~7654 3210
  ---------
  .M31 .2S0
   +++--+|+- Select 16 KiB PRG-ROM bank at CPU
   |     |   $8000-$BFFF and $C000-$FFFF (notice the bit order)
   |     +-- 0: Do not replace bit 0 (NROM-128)
   |         1: Replace bit 0 with CPU A14 (NROM-256)
   +-------- 0: Use PRG bank from MMC3; ignore $6000 bits 0-3/5
             1: Ignore PRG bank from MMC3; apply $6000 bits 0-3/5

MMC3-compatible registers ($8000-$FFFF)

$8000 index written   MMC3 register meant
-------------------   -------------------
0                     0
1                     3
2                     1
3                     5
4                     6
5                     7
6                     2
7                     4

Bits 6 and 7 of the value written to $8000 are unchanged. See MMC3 for further details.

Similar Mappers

• iNES Mappers 114 and 115 move the $5800 register to $6000 while rearranging its bits and add an outer CHR-ROM bank register at $6001. Mapper 114 keeps the MMC3 index register scrambling (using the same pattern) and adds register address scrambling, while Mapper 115 drops all scrambling.