08 July 2017, 20:12 | #1 |
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Double Pal Question
If I'm right, I've read that with doublepal dma cicles will double. Is that correct? How is possible?
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08 July 2017, 21:07 | #2 |
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No.
Double mode = scanline length is halved, number of lines is doubled. Number of DMA slots stays about the same. |
08 July 2017, 21:13 | #3 | |
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What are your doubts? [and yes, as Tony said logically the DMA slots stay the same only differently distributed I've checked in WinUAE HTOTAL=$79 VTOTAL=$24D In PAL we have HTOTAL=$E2 VTOTAL=$137($138)] ] Cheers, ross Last edited by ross; 08 July 2017 at 21:23. Reason: [] |
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09 July 2017, 16:03 | #4 | |
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09 July 2017, 17:23 | #5 |
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Paula work every time at the same frequency (CCK).
But sample periods can be minor due to more frequent DMA 'recharge'. It's directly related to HTOTAL: everytime H counter wrap we have two sample per channel that DMA can load (i've semplified, the concept is that). Smaller HTOTAL greater Paula reproduction frequency possible Ciao, ross |
09 July 2017, 18:39 | #6 | |
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09 July 2017, 19:17 | #7 |
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Paula (or anything else) does not take any advantage of it. It is just way the system works, DMA slots have static positions at the beginning of each scan line.
The shorter the scanline, the less time it takes until next scanline and another set of DMA slots |
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