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Old 06 January 2020, 14:36   #12
8bitbubsy
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Join Date: Sep 2009
Location: Norway
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Quote:
Originally Posted by Toni Wilen View Post
Is there only single period value that does it? Does every channel have slightly different value that does it?
All periods low enough to make the DMA unstable for the channel should work. Somewhere around period 1-123 depending on the channel index.
EDIT: This is apparently not true, I can't trigger it at certain low periods. Around period 114..123 seems more correct.

I just used period 120 (29.5kHz) on all channels to make a safe trigger and to playback a sample without too much pops/cracks.
Maybe it's possible to trigger this with safe periods too by finding other magic LEN1/LEN2 values. That would be amazing, but I doubt it's doable.

I successfully crafted two test programs and included source code:
1) "paulaquirk" will just play everything that is in chipmem after the program itself.
2) "paulaquirk2" plays a 500K sample that is incbin'd after the program, and then whatever comes after the sample in chipmem. This one is useful for quickly checking if the trick works or not in WinUAE.

https://16-bits.org/etc/paulaquirk.zip

Keep in mind that these two will play extremely unsatisfying junk waveforms, so be sure the volume is not loud.

Last edited by 8bitbubsy; 06 January 2020 at 14:58.
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