Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!bbn!bbn.com!levin
From: levin@bbn.com (Joel B Levin)
Newsgroups: comp.sys.mac
Subject: Re: Low-Cost Macintosh
Message-ID: <51783@bbn.COM>
Date: 6 Feb 90 19:58:36 GMT
References: <126900165@p.cs.uiuc.edu> <43100015@uicsrd.csrd.uiuc.edu> <19157@dartvax.Dartmouth.EDU> <131305@sun.Eng.Sun.COM>
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Reply-To: levin@BBN.COM (Joel B Levin)
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In article <131305@sun.Eng.Sun.COM> fiddler@concertina.Sun.COM (Steve Hix) writes:
|Any reason why a new, low-cost Mac couldn't be designed to take memory
|in integer multiples of SIMMs?  Is there some reason that the Plus *had*
|to be designed to take them in pairs only?  Or was it just easier to
|implement that way?

It would be a lot slower and need fancy circuitry.  A SIMM only has 8
DRAM chips on it, so to do a 16-bit access (like the 68000 wants to
do) it would need to access each DRAM twice.  With two SIMMs, you can
hit 16 DRAMs at once and get at all your bits in one go.

(And with the 68020/30/40 32-bit bus, you need to go 4 SIMMs at a time.)

	/JBL
=
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