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Old 06 August 2007, 17:54   #13
Toni Wilen
WinUAE developer
Join Date: Aug 2001
Location: Hämeenlinna/Finland
Age: 45
Posts: 23,640
Blitter linedraw cycle "secret" found (more later..)

Same line draw (1,0) to (30,20)

With singledot: BLTCON1 SING-bit set
Without singledot: BLTCON1 SING-bit cleared (only one pixel/horizontal line, used when area needs to be filled)

line 1: vsync
line 2: hsync
line 3: chip ram dma access
line 4: chip ram read/write access

As the diagram shows, only drawn pixels are written back (bus is free for other uses when no pixel drawn) I thought blitter always writes data back, even if there is no pixel drawn..

I think this explains problems with demos with vector objects because WinUAE's linedraw uses too many cycles depending on line type.. (testing soon)
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Name:	blit_without_singledot.png
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