INES Mapper 151: Difference between revisions
(Describe problems had here http://forums.nesdev.com/viewtopic.php?p=109949#p109949) |
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However, no Vs. System games have more than 64KiB of CHR to verify the correct behavior against, and it is unlikely that a separate ASIC was made just for Vs. System games. | However, no Vs. System games have more than 64KiB of CHR to verify the correct behavior against, and it is unlikely that a separate ASIC was made just for Vs. System games. | ||
Pictures of | Pictures of relevant Vs. System modules ([http://www.johnsarcade.com/nintendo_vs_ppu_info.php here] or [http://playchoice.riemen.net/vs_list.html here]; scroll down to "Vs. Gradius" or "Vs. The Goonies") show the same VRC1 as in [http://bootgod.dyndns.org:7777/profile.php?id=3040 NesCartDB] | ||
Revision as of 18:58, 24 July 2013
iNES Mapper 151 represents the VRC1 on the Vs. System. Given that iNES has a bit to mark "For Vs. System", this assignment was erroneous and any games marked thus should be iNES Mapper 075 instead.
Some emulators treat this as "mapper 75 with hardwired mirroring", rather than letting the "four screen" or "Vs. System" flags override mapper 75's normal ASIC-controlled mirroring. Since Vs. System by definition has 4K of NTRAM, and no other games are known that rely on this definition of hardwired mirroring, separating these mappers seems artificial.
It is remotely conceivable that this is not true: FCEUX-2.1.5's and Nestopia-1.4.0's implementations of mapper 151 do not attach the 5th bit of CHR bank onto the lower 4 and instead emulate all registers as 8 bits wide.
However, no Vs. System games have more than 64KiB of CHR to verify the correct behavior against, and it is unlikely that a separate ASIC was made just for Vs. System games.
Pictures of relevant Vs. System modules (here or here; scroll down to "Vs. Gradius" or "Vs. The Goonies") show the same VRC1 as in NesCartDB
