Startup IPI (was: Re: test13-pre3)
Quoted 8 lines · Maciej W. Rozycki
Quoted 2 lines
it kills machine; only problem is that
0x1300wr-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 find0x1300cycles 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 ?
Quoted 5 lines
Quoted 2 lines
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 [email protected]
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Quoted 1 line · Petr Vandrovec
/usr/bin/timesays that program runs for 3.40 - 3.56secs, so after dividing
Well, the test looks reasonable if the system load is low. Still the
performance is surprisingly low -- after changing the transfer width to 16 bits I ran the test on my dual P5MMX system equipped with an old ISA VGA card and I achieved 10.74ms for VGA RAM accesses and 586.6us for uncached main memory accesses.
Quoted 2 lines
by 1000 I get 3.4ms... Maybe I should complain to VIA or to Matrox that it is piece of crap ?
For VIA -- definitely. I don't think Matrox is at fault, though.
Quoted 3 lines
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...
At least ServerWorks claims they are willing to cooperate with us
although results seem to be questionable so far...
Maciej
Signature · 8 lines
+ Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: [email protected], PGP key available + - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] Please read the FAQ at http://www.tux.org/lkml/