INES Mapper 074: Difference between revisions

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(Rewrite based on cartridge observation.)
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=Notes=
=Notes=
* NES and older versions of VirtuaNES EX/Plus use mapper 74 to denote ''any'' MMC3-based mixed CHR-ROM/CHR-RAM game by simply making ''all'' of CHR-ROM writable, even if those games actually use [[iNES Mapper 191|191]], [[iNES Mapper 192|192]], [[iNES Mapper 194|194]], or [[iNES Mapper 195|195]]. This approach fails in the case of ''甲A - China Soccer League for Division A'', as the game writes all zeros to whatever CHR-ROM banks are mapped at power-on, overwriting CHR-ROM data in the process. As a result, the publicly available dump of that game (PRG-ROM CRC32 0x78FB3ED6) has been modified to remove those writes.
* SMYNES and older versions of VirtuaNES EX/Plus use mapper 74 to denote ''any'' MMC3-based mixed CHR-ROM/CHR-RAM game by simply making ''all'' of CHR-ROM writable, even if those games actually use [[iNES Mapper 191|191]], [[iNES Mapper 192|192]], [[iNES Mapper 194|194]], or [[iNES Mapper 195|195]]. This approach fails in the case of ''甲A - China Soccer League for Division A'', as the game writes all zeros to whatever CHR-ROM banks are mapped at power-on, overwriting CHR-ROM data in the process. As a result, the publicly available dump of that game (PRG-ROM CRC32 0x78FB3ED6) has been modified to remove those writes.
* 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.
* 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.
* [[iNES Mapper 119]] is Nintendo's first-party analog. Mappers [[iNES Mapper 252|252]] and [[iNES Mapper 253|253]], also used for Waixing's localizations, are similar but use a VRC4.
* [[iNES Mapper 119]] is Nintendo's first-party analog. Mappers [[iNES Mapper 252|252]] and [[iNES Mapper 253|253]], also used for Waixing's localizations, are similar but use a VRC4.

Revision as of 10:49, 14 September 2019

iNES Mapper 074 denotes the 43-393/860908C PCB, used by several games from Waixing:

  • 機甲戰士 (Jījiǎ Zhànshì, Chinese translation of Data East's Metal Max)
  • 甲A - China Soccer League for Division A
  • '#第四次: 机器人大战 - Robot War IV

The circuit board mounts an MMC3 clone together with a 74LS138 and 74LS139 to redirect 1 KiB CHR-ROM banks #8 and #9 to 2 KiB of CHR-RAM.

Notes

  • SMYNES and older versions of VirtuaNES EX/Plus use mapper 74 to denote any MMC3-based mixed CHR-ROM/CHR-RAM game by simply making all of CHR-ROM writable, even if those games actually use 191, 192, 194, or 195. This approach fails in the case of 甲A - China Soccer League for Division A, as the game writes all zeros to whatever CHR-ROM banks are mapped at power-on, overwriting CHR-ROM data in the process. As a result, the publicly available dump of that game (PRG-ROM CRC32 0x78FB3ED6) has been modified to remove those writes.
  • 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.
  • iNES Mapper 119 is Nintendo's first-party analog. Mappers 252 and 253, also used for Waixing's localizations, are similar but use a VRC4.
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