Messages in this thread |  | | From | "Petr Vandrovec" <> | Date | Wed, 20 Dec 2000 20:29:13 MET-1 | Subject | Re: Startup IPI (was: Re: test13-pre3) |
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On 20 Dec 00 at 19:52, Maciej W. Rozycki wrote: > > it kills machine; only problem is that 0x1300 wr-rd cycles to VGA apperture > > take 3.48ms, and this does not correspond with needed 200us udelay. > > Hmm, how do you calculate the time? Assuming AGP4x runs at 133MHz and a > read or write cycle lasts for a single clock tick (I don't know exact AGP > specs -- please correct me if I'm wrong), I find 0x1300 cycles to finish > in about 73usecs. The loop execution overhead may double the result and > it will still fit within 300usecs.
It is easy: int mfd; volatile unsigned long* memory; int i;
mfd = open("/dev/mem", O_RDWR); memory = mmap(0, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, mfd, 0x000B8000); close(mfd); for (i = 0; i < 0x1300 * 1000; i++) { *memory = i; *memory; } munmap(memory, 4096);
/usr/bin/time says that program runs for 3.40 - 3.56secs, so after dividing by 1000 I get 3.4ms... Maybe I should complain to VIA or to Matrox that it is piece of crap ? > > Without VIA datasheet I cannot try to disable some PCI features to find > > which one is culprit, so I'm sorry. > > But you may complain to the manufacturer and/or change hardware. I'm > still uncertain the delay should stay in...
My order was simple: no rambus memory, dual PIII at least on 800MHz and UDMA66. Yes, maybe I should buy ServerWorks instead of VIA, but I hoped... Best regards, Petr Vandrovec vandrove@vc.cvut.cz - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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