Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!gem.mps.ohio-state.edu!apple!dwells
From: dwells@Apple.COM (Dave Wells)
Newsgroups: comp.sys.mac
Subject: Re: Upgrade Memory on SE/030
Keywords: IIci, RAM, SIMMs
Message-ID: <35282@apple.Apple.COM>
Date: 4 Oct 89 22:42:34 GMT
References: <12679@orstcs.CS.ORST.EDU> <35202@apple.Apple.COM> <1989Oct3.144854.24428@agate.berkeley.edu> <35221@apple.Apple.COM> <14877@bloom-beacon.MIT.EDU>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 31

In article <14877@bloom-beacon.MIT.EDU> captkidd@athena.mit.edu (Ivan Cavero Belaunde) writes:
>In article <35221@apple.Apple.COM> dwells@Apple.COM (Dave Wells) writes:
>>Yes, it's true.  The Macintosh IIci is the first to allow the RAM in bank B
>>to be of higher density than the RAM in bank A.  In fact, you can install RAM
>>in bank B and take the SIMMs out of bank A and the Macintosh will work fine.
>>(Minus built-in video, which uses RAM from bank A.)
>>
>>This fantastic new functionality :-) is enabled by the new Memory Decode Unit
>>chip that replaces the old GluChip from previous Macintosh II models.
>
>Correct me if I'm wrong, but I was under the impression that the reason this
>is an important feature is that cycle-stealing for the built-in video slows
>down access to memory in bank A.  The ability to have higher density memory
>in bank B rather than bank A should then result on a lesser performance
>degradation when using built-in video.  If you have 5MB of RAM, and you put
>4MB on bank A and 1 on bank B (the only possible configuration before),
>the 4MB will be "slower memory" than the 1MB.  Thus it is useful and
>desirable to put higher density RAM in bank B when using built-in video.
>
>-Ivanski

You're absolutely correct.  I wasn't saying why you might do something.  Only
that it is possible, and what changed to allow it.

-Dave

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  Dave (Gimme more MHz) Wells, Apple Computer, Inc.  MS: 37-Y  (408) 974-5515
          Mail: dwells@apple.com or AppleLink d.wells or GEnie D.WELLS
 These opinions may be nothing more than the ramblings of a fatigued tinkerer
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