Date: Sun, 5 Oct 1997 21:40:11 +0600 (ESD) From: "Serge A. Babkin" <babkin@hq.icb.chel.su> To: rjs@fdy2.demon.co.uk (Robert Swindells) Cc: hackers@freebsd.org Subject: Re: PCI slowness ? Message-ID: <199710051540.VAA09237@hq.icb.chel.su> In-Reply-To: <199710051035.LAA00326@fdy2.demon.co.uk> from "Robert Swindells" at Oct 5, 97 11:35:25 am
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> > > > The chipset is Intel Triton on some chineese motherboard > > with 75MHz Pentium, memory is 60ns EDO. > > Theoretical PCI throughput is 33M > > of 4-byte transfers per second (the card claims to work > > in burst mode). Theoretical memory throughput is at least > > 10M of 4-byte transfers per second if we suppose that > > the memory cycle with all overhead is 100ns and the > > card reads by 4 bytes at a time. But the experiment > > shows throughput of only 17MBps or 4.25M of 4 byte > > transfers. Does the processor eats all the remaining > > throughput (although I think it must load most of the > > code it runs at idling into the cache) ? > > I thought that a 75MHz Pentium ran the PCI bus at 25MHz, not 33MHz. > > Are you sure that the bus on your system is at 33MHz ? No, I am not. But the motherboard has possibility to generate 33MHz and if I were the designer of this card I would use this clock independently of the processor clock. -SB
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