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From: dclemans@mentor.com (Dave Clemans @ APD x1292)
Newsgroups: comp.sys.atari.st
Subject: Re: Aerco 4 Meg ram upgrade boards
Message-ID: <1990Jan3.220950.470@mentor.com>
Date: 3 Jan 90 22:09:50 GMT
References: <131@van-bc.UUCP>
Organization: engr
Lines: 25

From article <131@van-bc.UUCP>, by johna@van-bc.UUCP (John Altstadt):
> 
> Does anybody have any information on how to add 1 Meg chips to the
> Aerco "easieST" solderless ram upgrade for a 520?  The literature
> that came with the board claimed that the board would hold up to
> 4 Meg, but neglected to state how the extra ram should be added to
> the sockets provided.  Since I could not afford the 1 Meg ram chips
> when I bought the kit, I didn't bother finding out how it was done.

While the Aerco board can be upgraded to 4mb, it is NOT just a simple
matter of swapping chips (at least for the early boards that this
message talks about).  There are a number of traces that have to be
cut, jumpers that have to be added, resistors that have to be swapped,
etc.  The upgrade instructions were on the order of 10-20 pages.

Note that the above doesn't apply for a 2.5 meg system; those were
just chip swaps.

To go to four megabytes, you have to cut traces/add jumpers to allow
one of the memory banks to take 1mb chips (256kb chips and 1mb chips
are not pin compatible; the Aerco board was shipped with one bank
set up for 256kb chips, and the other bank set up for 1mb chips;  to
goto 4mb you have to rewire the bank that was set up for 256kb chips).

dgc