INES Mapper 003

iNES Mapper 003 is used to designate the CNROM board and a very similar board used for Panesian games, generalized to support up to 255 banks (2040 KiB) of CHR ROM.

 Here are Disch's original notes:
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 =  Mapper 003          =
 ========================
 
 aka
 --------------------------
 CNROM (and compatible)
 
 
 Example Games:
 --------------------------
 Solomon's Key
 Arkanoid
 Arkista's Ring
 Bump 'n' Jump
 Cybernoid
 
 
 Registers (**BUS CONFLICTS** sometimes):
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   $8000-FFFF:  [CCCC CCCC]
     CHR Reg (selects 8k @ $0000)
 
 
 Notes:
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 CNROM has bus conflicts, however mapper 003 is meant to be CNROM and compatible.  So some mappers which were
 similar in function, but did not have bus conflicts are included.
 
 Additionally, CNROM's reg is only 2 bits wide... therefore it is capped at 32k CHR.
 
 So to be "safe":
  - for homebrewing:  assume bus conflicts, do not exceed 32k CHR
  - for emudev:  assume no bus conflicts, use all 8 reg bits
 
 There is no PRG swapping.
 
 
 The game Cybernoid seems to behave very strangely.  It uses unprepped system RAM... and it is as if it
 actually relies on bus conflicts (AND written value with value read from address)!