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Newsgroups: comp.sys.mac.hardware
Path: cantaloupe.srv.cs.cmu.edu!rochester!udel!wupost!howland.reston.ans.net!zaphod.mps.ohio-state.edu!sdd.hp.com!decwrl!apple!mumbo.apple.com!pcnntp.apple.com!gateway.qm.apple.com!Dale_Adams
From: [e-mail] (Dale Adams)
Subject: Re: 72-pin SIMMS for Q-800, be careful before buying
Sender: [e-mail]
Message-ID: <[e-mail]>
Date: Thu, 22 Apr 1993 19:19:47 GMT
References: <[e-mail]>
Organization: Apple Computer, Inc.,  Cupertino, CA
Lines: 22

In article <[e-mail]> Marty Sachs 
<[e-mail]> writes:
> I purchased 2x8 MB 72-pin (60 ns) SIMMs for my Quadra 800 from Chip
> Merchant (I've been very satisfied with them in the past).  Either one
> alone works, but both together fail.  I called Apple for advice and was
> told that there was a problem with "Composite" SIMMs.  Only non-composite
> SIMMs should be used with the Q-800.  Chip Merchant confirmed that they
> presently sell only composite 72-pin SIMMs.  So, Q-800 SIMMs need to be
> both 60 ns and non-composite.

8 MB SIMMs do not have to be composite SIMMs, although many (most?) 16 MB 
SIMMs are.  72-pin SIMMs allow two memory banks per SIMM, thus permitting 
the use of 4 Mb DRAM devices (the same ones used on 4 MB SIMMs) to be used 
for two 4 MB banks on one SIMM.  I can't imagine that it would be cheaper 
to build an 8 MB SIMM using 1 Mb DRAMs as the 4 Mb parts reached (and 
exceeded) bit for bit price parity with the 1 Mb parts some time ago.  
It's probably possible to build a single-bank 8 MB SIMM using 4 Mb parts - 
this could cause problems in a Q800.  I'm not sure why you'd want to do 
this, though, as a dual-bank 8 MB SIMM would be cheaper to build than a 
single-bank composite one.

- Dale Adams