INES Mapper 178: Difference between revisions
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[[Category:iNES Mappers|178]] | [[Category:iNES Mappers|178]][[Category:Mappers using $4020-$5FFF|178]] | ||
VirtuaNesEX sources call this mapper "Education / WaiXing / HengGe". However, virtuanes is among most other emulators in not supporting it fully; a game "Pet Family ES-1081" has a larger PRG than this mapper was originally supposed to handle, and only Nestopia 1.40u4 has been supporting it. The rest of the emulators will manifest a bug in the nametables when the main game engine starts. With r2536, FCEUX supports it; bizhawk does as well. | VirtuaNesEX sources call this mapper "Education / WaiXing / HengGe". However, virtuanes is among most other emulators in not supporting it fully; a game "Pet Family ES-1081" has a larger PRG than this mapper was originally supposed to handle, and only Nestopia 1.40u4 has been supporting it. The rest of the emulators will manifest a bug in the nametables when the main game engine starts. With r2536, FCEUX supports it; bizhawk does as well. | ||
Revision as of 19:29, 30 July 2013
VirtuaNesEX sources call this mapper "Education / WaiXing / HengGe". However, virtuanes is among most other emulators in not supporting it fully; a game "Pet Family ES-1081" has a larger PRG than this mapper was originally supposed to handle, and only Nestopia 1.40u4 has been supporting it. The rest of the emulators will manifest a bug in the nametables when the main game engine starts. With r2536, FCEUX supports it; bizhawk does as well.
This is a simple mapper.
$4800: [.... ...M]
M = Mirror mode
%0 = Vertical
%1 = Horizontal
$4801: [...P PPP.]
P = Some bits of the selected 32K PRG bank
$4802: [pppp pppp]
p = Some more bits of the selected 32K PRG bank
The selected 32K PRG bank (mapped to $8000) is P + (p<<2). The older emulators are masking this result by & 0xF which is what breaks the larger PRG games. It is unclear whether this mask is necessary for some games to work.
This addition is pretty weird. And, unlikely, I think. Pet Family seems to boot up and get past the nametable bug using an OR instead of a + which strikes me as much more likely.
The new PRG bank is only committed when $4801 is written. Therefore, you should write $4802 first and then $4801 to complete the remapping.
