Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!sharkey!sbcs!sbstaff2!altman
From: altman@sbstaff2.cs.sunysb.edu (Jeff Altman)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 386 Memory question (simms)
Keywords: simms 386
Message-ID: <9569@sbcs.sunysb.edu>
Date: 31 May 90 19:01:21 GMT
References: <5923@buengc.BU.EDU> <4922@plains.UUCP> <1990May31.010851.20237@cs.uoregon.edu>
Sender: news@sbcs.sunysb.edu
Organization: State University of New York at Stony Brook
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In article <1990May31.010851.20237@cs.uoregon.edu> akm@comix.cs.uoregon.edu (Anant Kartik Mithal) writes:
>In article <4922@plains.UUCP> kperson@plains.UUCP (Kerry Person) writes:
>>In article <59uengc.BU.EDU> rem@buengc.bu.edu (Robert E. Mee) writes:
>>>I have a question about memory configurations
>>>for a 386 system. I'm about to buy an SX that
>>>comes standard with 1mb in 4 256k simms. I asked
>>>the salesperson if it was possible to have 1
>>>1mb simm in it's place. He went on to say that 
>>>in order to use 1mb simms I have to use a minimum
>>>config of 4 meg!!!
>>>Is this correct?
>
>I think Kerry's analysis is correct for a system with 32 bits, like a
>386DX, *not* a 386SX, which has only 16 bits. Each simm should store
>*8* bits of data, not 4, so you should require 2 simms at a time.

Well, I have an opinion which conflicts.  At least on MCA machines,
you can install the memory in whatever fashion you wish.  Whenever the 
memory installation changes you are required to run a Reference Disk
to determine the new memory configuration.  The memory can be 4 256k 
simms, or 1 MB Simm or 2 1 MB simms, etc.  

The only requirement on the IBM PS/2s is that all of the chips be of 
the same type.  In other words, you can't replace one of the 256k 
simms with one 1 MB simm, or have 2 1MB simms and 2 2MB simms.

It is at the point of mixing chip types at which the hardware 
would have to be significantly altered.

People who own PS/2s should be very careful about listening to dealers
about memory upgrades.  This is because the types of memory installed
in a particular model is determined by the size of the hard drive 
originally installed in the machine.  For instance, the model 30 286
comes with 512k in two 256k simms when a 20MB drive is purchased, as opposed 
to one 1 MB simm when a 30 MB drive is purchased.
The same for the model 55SX, the 386sx machine.  With a 30 MB drive the 
machine has two 1MB simms, however with the 60MB drive it comes with
one 2 MB simm.  Most dealers are unaware of this and therefore will 
recommend the wrong memory kits.  

In particular, is the question of the necessity of ordering a 2MB-8MB 
memory expansion board for a memory upgrade.  If you have a 60MB drive 
55SX then you don't need it to expand to 4MB, however, if you have a 
30MB then it will cost you just as much to buy two 2MB simms and junk 
the two 1MB simms as it would be to purchase the expansion board.

So just be careful.

- Jeff (jaltman@ccmail.sunysb.edu)