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From: GR.MRB@isumvs.iastate.edu (MARK BERAN)
Newsgroups: comp.sys.zenith
Subject: Re: RAM simms
Message-ID: <1991Feb17.232750.16885@news.iastate.edu>
Date: 17 Feb 91 23:27:50 GMT
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Organization: Iowa State University, Ames IA
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In article <9102162212.aa03099@mc.lcs.mit.edu>,
STEPHEN@RPIECS.BITNET writes:
>
>>From: MARK BERAN <GR.MRB@isumvs.iastate.edu>
>
>>Zenith machines do not use any SIMMs that could be called unusual.
>>I did read an article in some journal or other that listed Zenith
>>amoung a hand-full of companies who used non-standard memory in an
>>attempt to keep selling their own over-priced memory.  That just
>>isn't true.
>
>Mark's list did not include the 386/16, Zenith's original 386, which
>does seem to use some kind of non-standard SIMMs.  Who knows their
>motivation for configuring the machines this way.  Perhaps it wasn't
>to sell their own over-priced memory.  Perhaps they just aren't very
>good at design.

The reason that I did not include the original 16MHz Zenith 386 is
because the topic was SIMMs.  The 386/16 did not use SIMMs.  Instead
it used proprietary 32-bit memory cards.  At the time this machine
was being developed, SIMMs were at best a new idea in micros.  So
in order to produce a machine with full 32-bit memory, and do this
using 256Kx1-bit and 1Mx1-bit chips which were available, Zenith
developed the proprietary 32-bit bus extension and cards to go with
it.  Amoung those cards were a 1M card fully populated with the
requisite 36 256Kx1-bit chips, and the 4M card fully populated with
the requisite 36 1Mx1-bit chips.  The remaining chips are memory
support logic, decoders, refresh circuitry, latches, etc.  On this
point, Zenith did very well for the time.  They did drop the ball
however on owners of these machines, as they held the price of
these cards high even though memory prices continued to fall.  Then
recently Zenith discontinued the 4M card.  There is no good reason
other than marketing that Zenith has not come up with a memory card
which would hold a useful number of 9-bit or 36-bit SIMMs.  They
have such a card in the ZA-3600-MQ (not sure about the MQ) for the
newer series of 386 machines, but it doesn't work in the old one.

I have and will continue to encourage Zenith to come up with a
solution for persons who own these machines.  But in the meantime,
standard 16-bit AT memory cards can be used, with the obvious side
effect of being much slower than those designed for the 32-bit
architecture of the machine.

Do I now of which I speak?  I hope so.  I am writing this response
on my own 386/16 at home, and have another one on my desk at work.
Not so quick or easy to upgrade as the 386/25 I use but hey.

Mark.