Xref: utzoo misc.forsale:7124 comp.sys.mac:36186 Path: utzoo!censor!geac!jtsv16!uunet!tut.cis.ohio-state.edu!purdue!bu-cs!bloom-beacon!mit-eddie!mit-amt!hkbirke From: hkbirke@mit-amt.MEDIA.MIT.EDU (Hal Birkeland) Newsgroups: misc.forsale,comp.sys.mac Subject: Re: 256K SIMMS forsale! Summary: rated vs/ actual SIMM speed Keywords: memory simm Message-ID: <461@mit-amt.MEDIA.MIT.EDU> Date: 9 Aug 89 18:18:00 GMT References: <460@mit-amt.MEDIA.MIT.EDU> <13347@polyslo.CalPoly.EDU> Reply-To: DarthVader@movies.media.mit.edu (Hal Birkeland) Followup-To: comp.sys.mac Distribution: usa Organization: MIT Media Lab, Cambridge MA Lines: 39 please note the followup line... IMHO, this discussion certainly does not belong in misc.forsale anymore... In article <13347@polyslo.CalPoly.EDU> dorourke@polyslo.CalPoly.EDU (David M. O'Rourke) writes: >adam@mit-amt.MEDIA.MIT.EDU (Adam Glass) writes: >>You're quite wrong. Mac II series computers will work just fine with 150ns >>SIMM chips. For all normal use, there is no apparent slow down at all. In [David's paragraph about Apple replacing "slow" SIMMS as a fix deleted] > Perhaps some hardware type on the net could explain why the 020 and 030 >in Apple's products require 120ns or better chips. Sorry, not quite a Mac hardware type yet... [.signature deleted] Chip manufacturers are conservative. They want 100% (or some number extermely close to this) of there chips to work at least as well as marked. In other words, a chip rated to 12MHz will often perform just fine at up to 16MHz (or higher if you are willing to hand pick). Testing is expensive in large quantities, apparently far more so than overly?-conservative speed ratings. 100% of all SIMMs rated for 150 ns will respond in at most 150 ns with valid output. This does not imply that they will respond in precisely 150ns, just before that. The DRAMs might be driving the output lines 30-50ns faster than that so the manufacturer gets the desired 100% yield. While not all 150ns SIMMs will work in a Mac II (I believe), quite a few if not most might. David is right when he says that Apple will replace the "too slow" SIMMs before anything else. Adam is right in saying many 150ns SIMMs will work in Mac IIs. hal@media-lab.media.mit.edu DarthVader@movies.mit.edu And may the Dark Side be with you No one would be foolish enough to claim any of my opinions, and they certainly are not expressive of my employers...