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From: tmp@doc.ic.ac.uk (Trevor Peacock)
Newsgroups: comp.sys.atari.st.tech
Subject: Homebrew SIMM expansion.
Message-ID: <2408@gould.doc.ic.ac.uk>
Date: 30 Oct 90 12:43:51 GMT
Sender: tmp@doc.ic.ac.uk
Organization: Dept. of Computing, Imperial College, London, UK.
Lines: 31


In my never ending quest for memory (without the price :^) I tried a simple 
experiment on my ST. 

What I did was to remove the 8 highest bits from bank 1 in my ST and wire up 
a SIMM socket so that the corresponding data, address, cas, ras & write lines 
went to those which the 41256's had occupied. 
I triple checked this, plugged a 256k SIMM into the socket, powered up and...
BINGO!! the ST couldn't see the top bank. 

I plugged the original 41256s back and then powered up to find that the top 
bank was there again. 
The SIMM was a 256k * 8 150nS (the original 41256s are 150nS).

I was hoping to find that this works, so that I could wire it all up and
buy some 1M SIMMs to plug in (with A9 wired up of course).

As I understand it, the SIMM should be equivalent to the 8 41256s, except that
the address, cas, ras & write lines are tied in parallel. I kept the wires as
short as possible etc, so I don't think that this was the problem.

Does anyone else have any experience with this - or any suggestions why it 
didn't work?

Trev..

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