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From: tgoose@eng.umd.edu (Jason Garms)
Newsgroups: comp.sys.mac.hardware
Subject: Re: IIsi memory upgrade questions...
Message-ID: <1991Apr5.054134.24924@eng.umd.edu>
Date: 5 Apr 91 05:41:34 GMT
References: <1991Apr3.234333.4056@parc.xerox.com>
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Reply-To: tgoose@eng.umd.edu (Jason Garms)
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Organization: College of Engineering, Maryversity of Uniland, College Park
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In article <1991Apr3.234333.4056@parc.xerox.com>, schneide@parc.xerox.com (Kris A. Schneider) writes:
 
> My si's currently got 2M (1M static + 4*256K SIMMs). 
Your IIsi does not have static RAM.  I think there is a confusion in terms.  Static RAM refers to RAM which is high speed (typically below 30ns) and consumes very little power.  This RAM is also very expensive.  What is in your machine is standard RAM (DRAM).  The confusion may be because this is soldered onto your logic board. (I guess and is therefore static ;->)

> Now, my understanding
> is that as long as the memory speeds are fast enough (90 or 100ns I think),
> I can mix'n match pretty much as I please.  So, my question is, if I plan
> on purchasing an additional 4M of memory, why wouldn't I just get a single
> 4M SIMM instead of 4*1M SIMMs?  Seems to me I'd end up with an additional
> 768K of memory onboard instead of collecting dust somewhere.  Although I
> haven't been pricing, it would also seem that a single 4M SIMM would be
> cheaper than 4*1M SIMMs, no?  Oh well, someone please set me straight!
NO, you cannot mix and match as you please.  Because of the way memory is addressed(on the Mac II models), it must be installed in banks of 4!  There are four slot inside your machine(which currently have 256k SIMMs in them).  Thus your upgrade options would be as follows:
	Remove the four 256k SIMMs and install:
		four 1MB SIMMs for a total of 5MB
		four 2MB SIMMs for a total of 9MB
		four 4MB SIMMs for a total of 17MB

no matter what you choose, the four 256k SIMMs become fairly worthless.

Jason Garms
tgoose@eng.umd.edu

P.S> The 256k SIMMs make nifty keychains and around Christmas time, put a hook on them and hang them on a tree!!! 8-)