INES Mapper 255

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iNES Mapper 255 is apparently assigned to the 110-in-1 multicart.

 A~[1BMZ PPPP  PpCC CCCC]
     ||| ||||  |||| ||||
     +-----------++-++++ - Select 8 KiB CHR at PPU $0000
     ||| ||||  ||
     +---++++--++------- - Select 16 KiB PRG at CPU $8000 and $C000 if Z=1
     +---++++--+-------- - Select 32 KiB PRG at CPU $8000 if Z=0
      |+---------------- - Select PRG bank size: 0-32K 1-16K
      +----------------- - Nametable mirroring: 0-PPUA10 ("vertical") 1-PPUA11 ("horizontal")

Hardware on the board includes

  • four 512 KiB ROMs for PRG
  • two 512 KiB ROMs for CHR
  • two 74'273 8-bit latches
  • 74139
  • PAL16L8 emulating a 74153
  • an unpopulated footprint for a 74'670

The two latches' reset inputs are tied to 5V, so the banking register boots with random contents.


This looks like a duplicate of iNES Mapper 225. It's not clear why Nestopia implemented it twice.

See also: https://forums.nesdev.com/viewtopic.php?p=209732#p209732