Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!samsung!uunet!visix!amanda From: amanda@visix.com (Amanda Walker) Newsgroups: comp.sys.mac.hardware Subject: Re: SIMMs for IIsi - what do I need? Message-ID: Date: 14 Dec 90 17:44:43 GMT References: <110992@convex.convex.com> Organization: Visix Software Inc., Reston, VA Lines: 34 In article <110992@convex.convex.com> woods@convex.com (Darrin Woods) writes: >100ns chips work just fine - go tell the tech to go back to school. >[...] All 4 SIMMS should be the same speed. >[...] Apple (and I) do not recommend mixing in a bank because of the >way that the mac uses the SIMMS in the bank. One SIMM will be receiving >(sorry, working with) info at 70ns and the other at 100ns, and it will >probably cause problems. > >Blacksheep >Senior Systems Engineer Bzzzzzt. Maybe you should go back to school too... :) This myth seems amazingly persistent in the Mac community. It makes no difference to anything except your pocketbook if a SIMM is faster than it needs to be. You can mix and match to your heart's content as long as each SIMM meets the *minimum* speed requirements. They just all have to be the same *size*. Pushing a SIMM faster than its rated speed can sometimes cause flakiness. Slower is not a problem. If you don't believe me, go to the closest engineering library or electronics distributor, find a manufacturer's databook, and read the data sheet for a dynamic RAM chip. The access time of a chip is simply the maximum amount of time that the chip is guaranteed to respond within. If a machine's memory circuitry is designed for a given speed of RAM, it just allows that much time before it reads the data off of the bus. If it's ready before that, it doesn't evaporate or anything :). -- Amanda Walker amanda@visix.com Visix Software Inc. ...!uunet!visix!amanda -- If we were meant to fly, we wouldn't keep losing our luggage.