On Sat, 4 Apr 2009 15:33:26 +0200 Rask Ingemann Lambertsen <r...@sygehus.dk> said:
> On Fri, Apr 03, 2009 at 09:14:16PM +0100, Ian Stirling wrote: > > Iain B. FIndleton wrote: > > > > I > > > wonder what the issue is in moving the frame buffer data? At the speeds > > > available on the FR, moving 640 x 480 x 2 = 614,400 bytes from memory to > > > a video buffer at 30 Hz needs about 18 MB/sec. > > > > > > What is the bandwidth for memory moves? > > > > About 6-8 or so - with 100% CPU utilisation > > There are four DMA channels in the s3c422b, so you shouldn't use the CPU > for straight memcpy() of such large blocks. The kernel doesn't yet support > mem->mem DMA transfers, but I'm working on that to use it in the glamo SD > card driver. that was tried. results were worse than with the cpu. try again - but.. been there, done that. ask dodji skeleti. :) 1. the memory bus is locked up anyway - be it cpu or dma cycles. if dma does it the cpu is still locked out, so it's not done async. 2. the actual performance was much worse - at best it was 1/2 the speed of using the cpu. but it was actually overall even worse on smaller blocks. -- ------------- Codito, ergo sum - "I code, therefore I am" -------------- The Rasterman (Carsten Haitzler) ras...@rasterman.com _______________________________________________ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community