Messages in this thread |  | | Date | Thu, 4 Oct 2001 14:31:18 +0200 (CEST) | | From | Etienne Lorrain <> | | Subject | Re: specific optimizations for unaccelerated framebuffers |
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--- Paul [private mail] wrote: > You might like to do some performance measurements on > X with a shadow framebuffer - see > > http://www.xfree86.org/4.1.0/apm5.html
This seems to still use the processor to copy the shadow buffer to the video memory, you will still have the PCI write stall...
> I have a machine with an SiS 630 where the video memory _is_ > main memory - the impact of the graphics processor continually > DMAing data for display is huge.
I am not speaking of DMA'ing at the refresh frequency (approx 70 times per second the complete video memory), just the modified 64Kb blocks, "once upon a while": if a single pixel is written twice, you will just see the latter written value on the screen - but who cares. Been able to DMA the complete video memory image around 5-10 times/second should be over the human eye sensitivity. Moreover this pixel will stay on the processor memory cache a lot longer, even without MTRR processors.
Etienne.
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