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From: mkant@a.gp.cs.cmu.edu (Mark Kantrowitz)
Newsgroups: comp.sys.mac
Subject: Macintosh Memory Upgrades [Summary]
Keywords: memory, SIMM, Macintosh, speed
Message-ID: <7954@pt.cs.cmu.edu>
Date: 12 Feb 90 22:30:04 GMT
Distribution: na
Organization: Carnegie-Mellon University, CS/RI
Lines: 84

This article summarizes the replies to my question about speed and
other factors for SIMMS for each of the Macintosh machines. Thanks to
clarson@ux.acs.umn.edu, meuchen@grad1.cis.upenn.edu (Paul Eric
Menchen), gbc@med.unc.edu (Geoff Crooks), craigm@wwu.edu (Craig
McDonald), and jdevoto@apple.com (Jeanne A. E. Devoto).

It was interesting to note that each gave me different information.
This summary represents what I believe is the correct information.

The definitive source is Apple's Tech Note 176, which is available in
BinHex 4.0 form from apple.com or sumex-aim.stanford.edu via FTP. You
will need Stuffit or BinHex4.0 to convert the files from Hex.

Send comments/corrections/suggestions to mkant@cs.cmu.edu

[1]  Chip Speed: 
	o  Minimum speeds for various machines:
		-  Mac+		150ns in banks of 2 (max 4MB)
		-  Mac SE	150ns in banks of 2 (max 4MB)
		-  Mac SE/30	120ns in banks of 2 (max 4MB)
		-  Mac II	120ns in banks of 4 (max 8MB)
		-  Mac IIx	120ns in banks of 4 (max 8MB)
		-  Mac IIcx	120ns in banks of 4 (max 8MB)
		-  Mac IIci	 80ns in banks of 4 (max 8MB)
	o  All will run with faster chips. 
	o  A faster speed will not help performance, as wait
	   states are hardwired.

[2]  Chip Types:
	o  The IIci requires FPM (Fast Page Mode) chips. 
	o  In the SE, DIP SIMMs may not leave enough room for
	   some expansion cards.
	o  Different speed chips may be mixed, as memory
	   access is synchronous. 
	o  Either 1x8 and 1x9 SIMMs may be used; the parity
	   chip is ignored in the standard Macintosh line.

[3]  Chip Configurations:
	o  In a given bank, the same density chips (256K SIMMs
	   Or 1MB SIMMs) must be used.
	o  So the following memory configurations work for a Mac+:
		Bank 1	Bank 2	Total Memory
		2 256K	------	512K
		2 256K	2 256K	1MB (standard configuration)
		2 1MB	------	2MB
		2 1MB	2 256K	2.5MB
		2 1MB	2 1MB	4MB
	o  For a Mac SE, swap banks 1 & 2 (this only matters in
	   the 512K and 2MB cases).
	o  For a Mac II, IIcx, and SE/30, you must upgrade
	   memory in 4 SIMM chucks, so only the following
	   configurations are possible:
		Bank A	Bank B	Total Memory
		4 256K	------ 	1MB
		4 256K	4 256K	2MB
		4 1MB	------	4MB
		4 1MB	4 256K	5MB
		4 1MB	4 1MB	8MB
	   Note that on the II, IIcx, and SE/30 there are no
	   resistors to cut. The larger chips must be in the
	   left bank.
	o  The IIci isn't as picky about which bank you put
	   the memory in (you can swap A & B), but there must
	   be memory in Bank A if you use the on-board video.
	o  For 4MB or 8MB SIMMs, you may have to wait either for
	   future versions of the Mac II, or for SIMM manufacturers
	   to include a PAL that intercepts certain Mac II signals
	   that cause the SIMMs to go into test mode (thereby
	   becoming very forgetful).

[4]  Where to get cheap chips: 
	o  The following two companies were recommended. People
	   said that they sell 70ns or 80ns SIMMs for less than
	   what most other places charge for 120ns chips. The phone 
	   number for Chip Merchant is from 800 information; no
	   800 number was listed for Technology Works. Both 
	   companies advertise in MacWorld, apparently.
		-  Chip Merchant 1-800-426-6375 
		-  Technology Works 
	o  Best price I've heard mentioned is ~$69/meg.



--mkant