Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!gem.mps.ohio-state.edu!tut.cis.ohio-state.edu!cica!iuvax!rutgers!att!cbnewsc!straka
From: straka@cbnewsc.ATT.COM (richard.j.straka)
Newsgroups: comp.sys.mac
Subject: Re: Nix on mixing memory speeds?
Message-ID: <3493@cbnewsc.ATT.COM>
Date: 27 Sep 89 13:01:29 GMT
References: <45d9e852.15840@valley.UUCP>
Reply-To: straka@cbnewsc.ATT.COM (richard.j.straka,ih,)
Distribution: usa
Organization: AT&T Bell Laboratories
Lines: 29

In article <45d9e852.15840@valley.UUCP| pfluegerm@valley.UUCP (Mike Pflueger) writes:
|In article <34977@apple.Apple.COM|, dwells@Apple.COM (Dave Wells) writes:
|| In article <11900@polya.Stanford.EDU| kaufman@Neon.Stanford.EDU (Marc T. Kaufman) writes:
|| |effect that: the folklore that says you can't mix memory speeds (subject to
|| |the requirement that each memory module is itself adequately fast) -- is
|| |Bullshit.
|Even if you use 150nS SIMMs with 40nS SIMMs, there is no problem - if the CPU
|hardware is designed for 150nS memory.  This is because the CPU puts out its

|I suspect Dave's experience with RAM problems were due to some other problem,
|maybe due to the Mac (Plus, II) borderline power supply designs/poor cooling.

Yes, the statement immediately above may very well be true since faster RAMs
(less nS) takes more power supply current.  Given the same manufacturer and
process, variations naturally occur in speed and power, which are inversely
related.  Across manufacturers and processes, all bets are off; you have to
look at the spec sheets.  But even then, that does not always tell all, since
they tell you the MAX power and MAX access times.

The bright side on this topic: It's probably a tertiary level effect.  I, for
one, even with a plus would not worry about 80 nS RAM in my machine.

PS: Yes the basic argument is true: almost all memory systems are synchronous
at some hardware level.  This means that you can mix speeds below that level
as long as you satisfy the basic max access time specs.
-- 
Rich Straka     att!ihlpf!straka

MSDOS: All the wonderfully arcane syntax of UNIX(R), but without the power.