INES Mapper 074: Difference between revisions

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'''iNES Mapper 074''' is a [[MMC3]] clone used in Eastern games.
{{DEFAULTSORT:074}}[[Category:iNES Mappers]][[Category:MMC3 with CHR ROM and CHR RAM]][[Category:Mappers with scanline IRQs]]
Like [[TQROM]], mapper 74 has CHR ROM on some CHR pages and CHR RAM on others.
'''iNES Mapper 074''' denotes the '''43-393'''/'''43-406'''/'''860908C''' PCB, used by several games from Waixing:
This is necessary because the large number of characters in the Chinese writing system precludes having them all in one CHR ROM bank, so they're copied into CHR RAM as needed.
* ''機甲戰士'' (Jījiǎ Zhànshì, Chinese translation of Data East's ''Metal Max'')
But instead of CHR pages 128 through 255 being RAM like in TQROM, only pages 8 and 9 are RAM.
* ''甲A - China Soccer League for Division A''
* ''第四次: 机器人大战 - Robot War IV''
* ''風雲 - Traitor Legend'' (original 1997 version)
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.


[[Category:iNES Mappers]]
=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 [[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.
* [[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.

Latest revision as of 09:20, 22 December 2023

iNES Mapper 074 denotes the 43-393/43-406/860908C 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
  • 風雲 - Traitor Legend (original 1997 version)

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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