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Path: sserve!newshost.anu.edu.au!harbinger.cc.monash.edu.au!msuinfo!uwm.edu!math.ohio-state.edu!sol.ctr.columbia.edu!news.kei.com!eff!news.umbc.edu!haven.umd.edu!cs.umd.edu!mojo.eng.umd.edu!nand.eng.umd.edu!chuckr From: chuckr@glue.umd.edu (Charles B. Robey) Newsgroups: comp.os.386bsd.misc Subject: Re: FreeBSD platform Date: 4 Jul 1994 02:51:16 GMT Organization: Project GLUE, University of Maryland, College Park, MD Lines: 30 Message-ID: <2v7tf4$ctj@mojo.eng.umd.edu> References: <2uacoc$gfi@reuter.cse.ogi.edu> <2ukb2g$r7b@huey.cc.utexas.edu> <Cs19IJ.B07@mozo.cc.purdue.edu> <2uo9ju$12b@reuter.cse.ogi.edu> <2v79ig$s8u@masala.cc.uh.edu> NNTP-Posting-Host: nand.eng.umd.edu X-Newsreader: TIN [version 1.2 PL1] Woody Jin (wjin@moocow.cs.uh.edu) wrote: : bj@staff.cc.purdue.edu (Ben Jackson) wrote: : > The 256K cache is *highly* recommended. I've heard that a DX2/66 is : > about 40% faster (wall clock time) with a 256K external cache. The : > Pentium supports 512k, and the extra 256K might be worth the $60-100 : > you'll pay for it. : What I read from an article some time ago was that the cache does not : affect any performance on multi-user platforms such as Unix, since : most PC boards use *direct mapped* cache. : Is there a motherboard which uses 4(or 8) way associative cache ? The thing with cache is, the more you have, the less each additional increment helps. I've seen some studies done, that make me wonder if anything over 128K is really of use. The key statistic is the hit rate of the cache, which means the percent of time that a memory read can be satisfied by a high speed cache read, instead of a slower main memory read. If you get a hit rate of over 90 percent at just over 128K (as the study I saw indicated) then the speedup you get from the additional cache is, at best, only speeding up a *max* of 10 percent of your reads; in reality, it's less, I think. I haven't read any Pentium studies, but I'd wonder if the expense really were worth it, to go to 512K. ----------------------------+----------------------------------------------- Chuck Robey | Interests include any kind of voice or data chuckr@eng.umd.edu | communications topic, C programming, and Unix. 7608 Topton St. | New Carrollton, MD 20784 | I run Journey2 (Esix SVR4) and n3lxx (FreeBSD) (301) 459-2316 | ----------------------------+-----------------------------------------------