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Using osbyte test for 4x SWRAM banks doesn't seem to work? #214

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kieranhj opened this issue Mar 29, 2018 · 1 comment
Open

Using osbyte test for 4x SWRAM banks doesn't seem to work? #214

kieranhj opened this issue Mar 29, 2018 · 1 comment

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@kieranhj
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Hoglet reported that he was able to start the game with a ROM in one of the BANKS (and link set appropriately) - this should have been picked up by the Master osbyte check but clearly wasn't.

@hoglet67
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It seems on the Master that OSBYTE A=&44 is actually implemented in DFS (ROM 9) (via the unrecognised OSBYTE service call) rather than the MOS. So if DFS is *UNPLUGGED then the result will not be correct. In fact, X=&FF is return, which PoP interprets as all sideways RAM banks available.

It's also worth noting that as Prince of Persia uses OSWORD A=&7F to do direct disk accesses, it's only possible to use MMFS (in ROM 8) if DFS (ROM 9) is unplugged. Otherwise DFS tries to handle the OSWORD calls, and everything hangs (with a black screen).

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