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From: wilko@idca.tds.PHILIPS.nl (W.C. Bulte)
Newsgroups: comp.sys.atari.st.tech
Subject: Re: stacking 256k simms
Message-ID: <835@idcapd.idca.tds.philips.nl>
Date: 16 Aug 90 07:01:13 GMT
References: <2190@gould.doc.ic.ac.uk>
Organization: Philips Information Systems, Apeldoorn, The Netherlands
Lines: 45

Newsgroups: comp.sys.atari.st.tech
Subject: Re: stacking 256k simms
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References: <2190@gould.doc.ic.ac.uk>
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In article <2190@gould.doc.ic.ac.uk> tmp@doc.ic.ac.uk (Trevor Peacock) writes:
>Has anyone tried (or even considered) using blocks of four 256k simms to give
>1Mb banks? Of course, this would require demultiplexing address line A9 into
>two bits to select one of the 256k blocks within the 1 meg bank. Has this
>be done? Is the ST's chippery able to handle the loading caused by the 
>simms being connected in parallel? (this would be a total of 8 per bank for a 
>4 Mb system, two groups of eight in parallel)  
>I'm sure this is a minefield of capacitance and timing problems, but would 
>like to know whether anyone has had any success.
>
>Trev..
>
>------------------------------------------------------------------------------
>Trevor Peacock,		 | Tel : 071 589 5111 X 5052 | JANET : tmp@uk.ac.ic.doc 
>Department of Computing, | DARPA : tmp@doc.ic.ac.uk 
>Imperial College,        \ or      tmp%uk.ac.ic.doc@nsfnet-relay.ac.uk
>180 Queens Gate,London SW7 2BZ |    UUCP : tmp@icdoc.UUCP or ..!ukc!icdoc!tmp
>
> 

Somebody did. I got a copy somewhere of a german magazine (ST Computer ??)
which describes such a memory extension. Indeed there is some logic involved 
to demux A9 and address the ram banks. Theoretically it ought to work, but 
with all the added wiring and chip capacitance I think it stinks..

We have enough problems with installing "simple" 1 Mbit chips as it is.
(Well, not all of us, but according to this newsgroup frequent enough).

_     ______________________________________________________________________
 |   / o / /  _   Wilko Bulte   Domain: wilko@idca.tds.philips.nl
 |/|/ / / /( (_)                uucp  : [mcsun,hp4nl]!philapd!wilko
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