INES Mapper 074

iNES Mapper 074 is a MMC3 clone used in Eastern games. It's identical to iNES Mapper 192 and used for the same reason, except that only pages 8 and 9 are RAM. If the NES 2.0 header is present, 74 and 192 should be emulated identically, as NES 2.0 specifies CHR RAM size elsewhere.

BizHawk supports this mapper as of r3973; FCEUX and FCEU-MM have supported them for a long time but definitely as of 26-nov-2012, although CRC checks for m192<->m074 may be lacking.

Many games are mis-headered as m074 but should really be one of 191, 192, 194, or 195 and will either need to be changed to the correct mapper, or changed to the correct amount of CHR RAM and handled by unified code.

Nestopia emulates all of Waixing's MMC3 clones with a slight variation on the mirroring control register at $A000, additionally treating a written value of 2 or 3 as 1scA and 1scB mirroring respectively.

 Example Games:
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 Di 4 Ci - Ji Qi Ren Dai Zhan
 Ji Jia Zhan Shi
 
 
 Notes:
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 This mapper is a modified MMC3 (or is based on MMC3?).
 
 In addition to any CHR-ROM present, there is also an additional 2k of CHR-RAM which is selectable.  CHR pages
 $08 and $09 select CHR-RAM, other pages select CHR-ROM

Mappers 252 and 253, also used for Waixing's localizations, are similar but use a VRC4.