Date: Thu, 18 May 1995 09:46:00 -0700 From: "Russell L. Carter" <rcarter@geli.com> To: phk@ref.tfs.com Cc: hackers@FreeBSD.org Subject: Memory bandwidth, was Adaptac 2940 Message-ID: <199505181646.JAA05785@geli.clusternet>
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|From: Poul-Henning Kamp <phk@ref.tfs.com> |Subject: Re: Adaptec 2940? |> > The drivers are identical, so the interupt time should be the same for |> > driving either card on the same machine. Your benchmark is not really |> > valid since they were run on different motherboards. |> |> To some extent. It is instesting that a good EISA system can best a |> poor PCI system. Woe to those buying cheap PCI motherboards. | |Oh, it's much worse than that. This is some numbers I have been collecting, |the represent the bandwidth between CPU and RAM pretty well: | |A RS6000/590, AIX 3.2.5 | # cc -o ram-speed -O3 ram-speed.c | # ./ram-speed | 49005fb0 0.116 uS/op 8.61e+06 op/S 32.833 Mb/S | 8938c0df 0.177 uS/op 5.64e+06 op/S 21.532 Mb/S | I don't know what to make of this. The 590 is capable of 4*8=32 bytes transferred from main memory per 62.5 MHZ clock. A simple matrix-matrix multiply will attain this. That's a hellava lot more than 32 MB/s. This system has had the best memory bandwidth of any non Cray Research system for the past year. There is a something like a "-power2" optimization switch that makes a lot of difference. Another memory benchmark that has been run on a lot of systems is STREAM, available from ftp://perelandra.cms.udel.edu/bench/stream. Results are in ftp://perelandra.cms.udel.edu/bench/stream/Tables/table.print My P5-100-TP4-PB/FreeBSD system is in there, looks pretty good against lower end SGIs and SUNs, but doesn't come close to the RS6000/590. Russell
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