notaz / picodrive

Fast MegaDrive/MegaCD/32X emulator
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Knuckles' Chaotix 1994-12-07 and 1994-12-27 prototypes do not boot #110

Open ehw opened 4 years ago

ehw commented 4 years ago

These are two prototypes of Knuckles' Chaotix that were released over a decade ago that originated from a QA archival backup disc, so these are not bad 'dumps' per se. Both can boot on hardware, but 1994-12-07 doesn't boot sometimes due to some bizarre timing issue (this can also be seen in Kega Fusion too, as soft resetting the ROM will sometimes boot the game as well). 1994-12-07, 1994-12-27, and 1994-12-30 contain sound issues in the PWM channel that are always replicated under emulation, but occurs randomly on hardware (this is due to the sound driver being meant for an earlier hardware revision and isn't exactly an emulation issue, so I wouldn't worry about this. just thought I'd mention it).

At the time these two prototypes were released, no emulator could properly emulate them except for Steve Snake's Kega Fusion. If I recall, Kega Fusion implements a different setting for CPU interleave between the two SH2s for Knuckles Chaotix. Steve had hard coded the checksums for the available ROMs at the time to select the appropriate setting for Chaotix. Since the prototypes were just released, a special version had to created that incorporated the hashes for the new prototypes. I believe Steve eventually added a setting in the officially released versions of Kega Fusion that incorporated the "Fast 32X Timing" which did pretty much the same thing.

It would be interesting to see if these can work in PicoDrive, as the last time these prototypes were really looked at were all the way back in 2008 when Steve was still updating Kega Fusion.