Xref: utzoo misc.forsale:7135 comp.sys.mac:36199
Path: utzoo!censor!geac!jtsv16!uunet!tut.cis.ohio-state.edu!cica!iuvax!truel
From: truel@iuvax.cs.indiana.edu (Bob Truel)
Newsgroups: misc.forsale,comp.sys.mac
Subject: SIMM speed rating (was Re: 256K SIMMS forsale!)
Keywords: memory simm
Message-ID: <24441@iuvax.cs.indiana.edu>
Date: 9 Aug 89 16:12:00 GMT
References: <460@mit-amt.MEDIA.MIT.EDU>
Reply-To: truel@iuvax.cs.indiana.edu (Bob Truel)
Distribution: usa
Organization: Indiana University, Bloomington
Lines: 38

In article <460@mit-amt.MEDIA.MIT.EDU> 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
>fact, you can't tell the difference between the two except if you have a
>SIMM tester or you happen to look at the chips.

I don't know about these new dynamic memory, but it used to be that speed
rating had nothing to do with how fast the chip did anything.  That
is, 150ns chips do not run slower than 120ns chips at all (as Adam suggested
in a previous post) only hotter at the same speed.  So 150ns chips should
run at the same temperature at 150ns as 120ns chips run at 120ns.  If you
run them faster then they will use up more energy and burn out.  

I am not sure whether your mac is at any risk from RAM burning out (I doubt
it) but it always seems a good idea to avoid potential disasters if
you are doing anything besides game playing on your mac.

Furthermore, this is the reason why 80ns chips will not speed up your mac.
The faster chips are still being fed the same clock cycle and so are still
running at ~120ns (although cooler).

If I had one improvement for the macintosh II hardware, it would be to
fix this.  With the 680x0 family's asynchronous bus, it would be a simple
matter to put the memory acknowledge hardware on the SIMMs themselves.
A chip full of buffers wired in series would give a good delay.  Of course
this would mean nonstandard SIMMs I suppose, but banks of SIMMs could have
jumpers on the motherboard for the same purpose.

Wait States:  Just say NO.




-- 
Robert N. Truel			"Life sucks, of course, but it didn't have
				 to suck quite like this" -- RJSJR
truel@silver.bacs.indiana.edu
truelr@iubacs.BITNET