Date: Mon, 04 Aug 1997 12:55:20 -0500 From: Tony Overfield <tony@dell.com> To: "Jonathan M. Bresler" <jmb@FreeBSD.ORG> Cc: cjs@portal.ca, freebsd@atipa.com, tom@sdf.com, hackers@FreeBSD.ORG Subject: Re: Pentium II? Message-ID: <3.0.2.32.19970804125520.0070d730@bugs.us.dell.com> In-Reply-To: <199708031631.JAA01116@hub.freebsd.org> References: <3.0.2.32.19970803041915.006a69e4@bugs.us.dell.com>
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At 09:31 AM 8/3/97 -0700, Jonathan M. Bresler wrote: >Tony Overfield wrote: >> I think many of the benchmarks indicate this. The benchmarks show, when >> run at the same clock frequency, that the Pentium II runs at speeds >> comparable to the Pentium Pro, even though the L2 cache is running at >> half-speed. Many folks had claimed that the Pentium II would be much >> slower because of the half-speed L2 cache. > > oh? what is the size of your dataset? what is the data access > pattern? without specifing these two items, i cant tell how > your are using L1 and L2 cache. Of course, that's obvious. But my point is that a larger L1 cache makes the Pentium II faster than it would have been otherwise, since it partly offsets the slower L2 cache. In many real-world situations, the dataset size and access patterns constantly change. A bigger L1 cache only wins whenever the L1 cache hit-rate is improved strictly because of its size. To believe that such a sitiuation never arises seems to me to be a losing position to take. > what we need is a benchmark that has a fixed data access pattern > and known data set size. better yet would be one that starts with > a very small data set and grows the data set till the computer starts > using disk. a graph of the results would show the speed of the > machine accross all its memory regimes. > > http://www.scl.ameslab.gov/scl/HINT/HINT.html Thanks for the pointer. The effect I'm describing seems to be visible in their data, especially if you select the "(double)" data. - Tony
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