🚀 go-pugleaf

In article <1989Oct3.144854.24428@agate.berkeley.edu> bmug@garnet.berkeley.edu (BMUG) writes:
>In article <35202@apple.Apple.COM> dwells@Apple.COM (Dave Wells) writes:
>>Yes, you can add 4 1MB SIMMs to your SE/30 to get a total of 5MB.  Only catch
>>is that you'll have to relocate the 256K SIMMs from bank A to bank B and put
>>the 1MB SIMMs in bank a.  This works like a charm.
>>
>>This is the same solution as for a Macintosh II, Macintosh IIx, and Macintosh
>>IIcx...
>
>We've heard that the IIci has an arrangement whereby it isn't necessary to
>relocate the 1 mb which comes with the machine to the "B" bank when adding
>SIMMs for more RAM.  Is this true?  Is it because new machines are
>shipping with the weird new quarter-MB SIMMs?
>
>Enquiring minds want to know...

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.  Besides
some other things, it removes the RAM configuration restrictions that were
present in previous Mac II's.  If you're wondering where it is on the logic
board, look for the large, square chip, under the SuperDrive, about halfway
between the front and the floppy cable socket.

The "weird new quarter-MB SIMMs" are just that.  Weird, quarter-MB SIMMs.
They use a different chip configuration because supplies of the normal chips
at 80ns was/is insufficient.

-Dave

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           Dave Wells, Apple Computer, Inc.  MS: 37-O  (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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