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Old 04 August 2014, 21:52   #5
Toni Wilen
WinUAE developer
 
Join Date: Aug 2001
Location: Hämeenlinna/Finland
Age: 42
Posts: 19,534
ppctest.dms WarpOS test now passes!

It seems INT_LVL isn't for allowing/not allowing interrupts, I think it is used to activate PPC interrupt: If any bit 0 to 6 is active in INT_LVL AND IPL_EMU is less than any active INT_LVL interrupt number AND P5_ENABLE_IPL is active: PPC CPU interrupt line becomes active. (active as in bit is cleared, active low).

This allows WarpOS test to work. It sets INT_LVL to 0x7f (all inactive), enables P5_ENABLE_IPL, sets IPL_EMU to 7 (IPL level 0). Later when 68k code wants to wake up PPC code, it clears INT_LVL bit 0. PPC interrupt code runs which sets it back to one.

PowerUP does it totally differently..

btw, I guess this method only works when 68K is interrupt master. (68k gets "real" Paula interrupts)
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