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Atari coding BBS
| Re: VBL Interrupt delay |
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Posted by: evil
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Oct,10.2012-20:59
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If your blitter pass does not end before the vbl ends, it will continue over and delay the next vbl interrupt. The same thing with HBL and MFP interrupts too. Once fired up, the blitter is a beast and won't stop before the pass is over, and everything else will have to stay patient and wait for bus access.
That's why there is a shared mode, with 256 cpu/blitter cycles in pair. In case the cpu doesn't have anything to do, it can fire up the blitter immediately instead of waiting the 256 cycles. Blitter passes becomes a bit slower (say 10% or so) but at least the cpu gets a chance to run interupt-code.
But I belive we went over this before? See old thread with example code
--
Anders Eriksson
ae@dhs.nu
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