Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!usc!julius.cs.uiuc.edu!ux1.cso.uiuc.edu!ux1.cso.uiuc.edu!bruner From: bruner@sp15.csrd.uiuc.edu (John Bruner) Newsgroups: comp.sys.mac.hardware Subject: Re: SIMMs for IIsi - what do I need? Message-ID: Date: 17 Dec 90 17:08:58 GMT References: <110992@convex.convex.com> <1990Dec15.035554.15172@eng.umd.edu> <111547@convex.convex.com> Sender: news@ux1.cso.uiuc.edu (News) Organization: CSRD, University of Illinois Lines: 17 In-Reply-To: woods@convex.com's message of 17 Dec 90 01:31:05 GMT In article <111547@convex.convex.com> woods@convex.com (Darrin Woods) writes: > Now sit in your > lab with a Mac, and put different speed SIMMS within a bank and test > out the circuits, that Mac cannot handle it. Vendors will sometimes supply parts that exceed their ratings (particularly as their process technology matures). Hence, a 100ns RAM chip might really be an 80ns chip. If the Mac really can't handle mixing RAM's of different speeds, then perhaps the only safe way to replace or add memory is to use SIMM's from the same lot. (Even then there may be speed variations among the chips.) Maybe this is the reason Apple puts 80ns memory in the new machines -- they can't count on all of the 100ns chips being the same speed...? -- John Bruner Center for Supercomputing R&D, University of Illinois bruner@csrd.uiuc.edu (217) 244-4476