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Old 08 September 2014, 19:30   #293
Toni Wilen
WinUAE developer
 
Join Date: Aug 2001
Location: Hämeenlinna/Finland
Age: 42
Posts: 19,559
About "UAE" devices and directory filesystem running under OS4:

Even if OS4 supports them (it should, at least in theory) but there are two technical problems:

m68k to host switching is done using m68k TRAP instructions, when UAE m68k emulator notices trap instruction executed by UAE boot rom, it calls host side code and trap instruction is not emulated. This can't work if m68k is not UAE m68k, PPC emulated m68k just executes trap instruction and bad things happen. Traps needs to be replaced with IO accesses to some reserved space (like UAE boot ROM). Quite easy update.

Much more complex problem: host side code takes parameters from UAE m68k emulator's registers which won't work when UAE m68k is idle and "m68k" is PPC emulated.. Each trap call needs to save parameters to memory and return code also needs to be memory based, not D0 register. This requires lots of really boring updates..

Only after everything else works. Maybe.
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