The Irem 74HC161/32 mapper configuration, used by several NES games from Irem, is the bastard child of UNROM and CNROM. Like UNROM, it switches 16 KB program banks (fixing $c000-$ffff to the last bank in the cartridge), but like CNROM, it carries tile data in a ROM that can only be swapped 8 KB at a time. It has been assigned iNES board class 78, but I haven't written any programs that use it, so I can't vouch for the accuracy of this information.

76543210  $8000-$FFFF
||||++++- Select 16 KB bank for PRG $8000,
||||      as in UNROM
++++----- Select 8 KB bank for CHR,
          as in CNROM

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