Date: Mon, 9 Dec 1996 23:36:46 -0800 (PST) From: "Rodney W. Grimes" <rgrimes@GndRsh.aac.dev.com> To: petzi@apfel.de (Michael Beckmann) Cc: dkelly@nexgen.HiWAAY.net, hardware@freebsd.org Subject: Re: Tyan Tomcat ? 256 MB RAM ? DIMMs ? Message-ID: <199612100736.XAA15216@GndRsh.aac.dev.com> In-Reply-To: <Pine.BSF.3.95.961209133706.21388B-100000@serv1.zsb.th-darmstadt.de> from Michael Beckmann at "Dec 9, 96 03:55:30 pm"
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> On Sun, 8 Dec 1996, David Kelly wrote: > > > IMHO, especially when you are dealing with 256M of RAM, buy FPM w/ > parity. The possible performance boost of EDO isn't worth the loss of > error checking. If you'll take a bit of a performance hit the Tomcat I > will do error correction on its memory. > > > > Others have posted to the FreeBSD lists that it is very difficult to > quantify a performance gain with EDO memory. > > Hmm, I am aware that there is only a small performance gain in EDO RAMs; > but many modern mainboards only support 4-3-3-3 burst with FPM, and e.g. > 4-2-2-2 burst with EDO; and that should make a difference, IMHO. Yea, okay, so EDO has a shorter burst timing, but that ONLY applies when you miss the L2 cache. Give a 85%+ L2 cache hit rate that means you get a 33% increase on 15% of your memory references (and ONLY if the CPU does a burst access, which is rare on a cache miss situation), best case number is 33% * 15% == 5%, actual measured test data using ``FreeBSD make world'' as a test case is less than 1%. One place I have heard that EDO really does make a difference is on bus mastered PCI access to main memory from things like video capture cards like the Matrox Meteor, and that is because these are not cached cycles, but other than that 1 exception I have not seen any ``real world'' or ``synthetic benchmarks'' that show EDO giving you more than a 1% performance increase. (oopppss.. if you don't have an L2 cache EDO is a real _BIG_ win, but then, who runs without L2 cache!!!) Folks, EDO is a joke, youv'e been sold a bunch of marking hype... > EDO is, however, not my primary interest, I would rather have a mainboard > with 4 - 8 DIMM slots, for standard 64 MB DIMMs as they are used in > Macintoshes, Suns etc. These are available everywhere for reasonable > prices. For the time being, however, a mainboard that can accept 8 x 32 MB > PS/2 modules would be just fine. > > Cheers, > > Michael > > -- Rod Grimes rgrimes@gndrsh.aac.dev.com Accurate Automation, Inc. Reliable computers for FreeBSD
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