 No.21846
hap Developer
Nov 20, 2023, 09:55
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It broke with this powerpc commit: https://github.com/mamedev/mame/commit/bced77dec95faea0a2adaa3de09dd1cb48b5ae92 |
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 No.21847
windyfairy Tester
Nov 21, 2023, 06:34
edited on: Nov 21, 2023, 06:35
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I looked into it and the games seem to rely on using an invalid form of the lmw command to work. In particular, rD starts at r0 and rA starts at r1 which even according to the PowerPC 603 manual is not valid ("The PowerPC architecture defines the load multiple word (lmw) instruction with rA in the range of registers to be loaded as an invalid form"). One thing I wasn't clear on when I implemented it and still am not clear on after checking the manuals again is how exactly an "invalid form" involving the registers clashing is actually handled. Since these games rely on the command to even function it doesn't seem like the invalid form is handled as an invalid opcode exception. Removing only the code that throws the invalid opcode/0x80000 exception lets these games boot again while also lets the originally broken game tropchnc to still boot. There's an issue here still in how to handle the invalid form so someone with more experience with PPC might be able to figure out the proper way to handle the invalid form of the command, but otherwise it probably wouldn't hurt to just remove the code that raises the exceptions. |
 No.21858
VasiliyFamiliya Tester
Nov 23, 2023, 06:27
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Now, if to possess oneself, in Battle Gear 2 it's possible to long last till the record screens (althought they're still absolutely blank) in the attract mode. |