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Photon · 30 September 2019, 16:29

I've edited my post. I will measure the time in CPU instructions executed across the vblank, and then I'll know exactly. I guess it should correspond to the $1a scanlines, but the actual time it takes for the monitor vsync pulse should be ~576ms = 9 rasterlines.

I guess my main point is that if you have interrupts running that change values you rely on, results could vary depending on when the interrupt hits in your running main code. And that if you have interrupts or a BLTPRI=1 blit running during a VPOS check with beq, it could be skipped so that you get a stagger.

30 September 2019, 16:29	#75
Photon Moderator Join Date: Nov 2004 Location: Eksjö / Sweden Posts: 5,629	I've edited my post. I will measure the time in CPU instructions executed across the vblank, and then I'll know exactly. I guess it should correspond to the $1a scanlines, but the actual time it takes for the monitor vsync pulse should be ~576ms = 9 rasterlines. I guess my main point is that if you have interrupts running that change values you rely on, results could vary depending on when the interrupt hits in your running main code. And that if you have interrupts or a BLTPRI=1 blit running during a VPOS check with beq, it could be skipped so that you get a stagger. Last edited by Photon; 02 October 2019 at 22:09.