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jotd · 29 January 2020, 17:17

I use to find mainloops all the time for instance to find levelskips or insert CD-music play. I have a good technique with WinUAE. Let me explain.

Play the game and break with shift+F12.

First get rid of the case where you're in an interrupt with "fi RTE", then "t". Unless there's a trap within an interrupt, that should get you back in non-VBL part of the game.

Note down the value of A7. Then use "fi" instruction to find next RTS and "t" to return from it. See if A7 increases. If it doesn't, that's because the RTS is from a subroutine. So ignore that one.

After a few moments, you find the highest A7 value. Means that you're in the main loop. Put breakpoints here and there to find the point beyond which the breakpoint doesn't hit. There's probably a label, and below a BRA to it.

29 January 2020, 17:17	#18
jotd This cat is no more Join Date: Dec 2004 Location: FRANCE Age: 52 Posts: 8,320	I use to find mainloops all the time for instance to find levelskips or insert CD-music play. I have a good technique with WinUAE. Let me explain. Play the game and break with shift+F12. First get rid of the case where you're in an interrupt with "fi RTE", then "t". Unless there's a trap within an interrupt, that should get you back in non-VBL part of the game. Note down the value of A7. Then use "fi" instruction to find next RTS and "t" to return from it. See if A7 increases. If it doesn't, that's because the RTS is from a subroutine. So ignore that one. After a few moments, you find the highest A7 value. Means that you're in the main loop. Put breakpoints here and there to find the point beyond which the breakpoint doesn't hit. There's probably a label, and below a BRA to it.