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AOROM was a board used on cartridges containing NES software developed by Rareware, such as Battletoads, Solar Jetman, and Jeopardy!. Its hardware, designated iNES mapper 7, It is one of the simpler mappers, with a 32 KB ROM bankswitch and CHR RAM, but it has a very important quirk: one-screen mirroring. Instead of placing the two nametables side-by-side or above each other as is done in most games, Rare games map only one nametable into the NES PPU's address space at once, often changing it mid-screen to switch between the game display and a status bar. Rare games will also expose flaws in your emulator's timing, in its palette code, and in its rules for writes to PPU register $2006 during horizontal blanking. That's part of why NESticle always needed a patch to be able to play Solar Jetman and some of the other more advanced games.

Don't touch NESticle with an 8 bit pole.

76543210  $8000-$FFFF
   |++++- Switch 32 KB PRG bank at $8000-$FFFF.  Either the
   |      long jump code (which sets a bank and calls a
   |      subroutine in that bank) will need to be present at
   |      the same place in all banks, or it will need to be
   |      in RAM.
   +----- One screen mirroring.  Select which of the two
          1 KB banks to use for mirroring.

(return to) iNES mappers

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