Date: Sun, 3 Aug 1997 09:31:07 -0700 (PDT) From: "Jonathan M. Bresler" <jmb> To: tony@dell.com (Tony Overfield) Cc: cjs@portal.ca, freebsd@atipa.com, tom@sdf.com, hackers@FreeBSD.ORG Subject: Re: Pentium II? Message-ID: <199708031631.JAA01116@hub.freebsd.org> In-Reply-To: <3.0.2.32.19970803041915.006a69e4@bugs.us.dell.com> from "Tony Overfield" at Aug 3, 97 04:19:15 am
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Tony Overfield wrote: > > At 03:10 PM 8/2/97 -0700, Curt Sampson wrote: > > > >On Sat, 2 Aug 1997, Tony Overfield wrote: > > > >> Since the hit rate of the L1 cache is usually much higher than that of > the L2 > >> cache, the effect of the slower L2 cache in the Pentium II is usually > offset > >> by the beneficial effect of not having to access it. So even at the same > >> clock rate, the Pentium II can run faster than the Pentium Pro. > > > >Do you have any benchmarks that indicate this? > > 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. 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 jmb > > It should be easy to agree that larger L1 caches have higher hit rates. In > turn, higher L1 cache hit rates reduce the demand on the L2 cache. Whenever > the Pentium II is hitting in the L1 cache strictly due to its larger size, it > will be faster. Whenever the Pentium II misses the L1 cache, it will be > slower. > > >Or are you just dreaming? > > I sure hope not. I wouldn't want to waste a dream on this stuff. :-) > > - > Tony > >
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