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From: cmv@ihuxz.ATT.COM (Craig Votava)
Newsgroups: comp.sys.att
Subject: Re: PC7300 upgrade question
Message-ID: <2077@ihuxz.ATT.COM>
Date: Mon, 18-May-87 13:00:14 EDT
Article-I.D.: ihuxz.2077
Posted: Mon May 18 13:00:14 1987
Date-Received: Tue, 19-May-87 04:39:06 EDT
References: <2069@arizona.edu> <168@gizzmo.UUCP>
Reply-To: cmv@ihuxz.UUCP (Craig Votava)
Organization: AT&T Bell Laboratories
Lines: 52
Keywords: UNIXPC PC7300 memory disks upgrade

About upgrading memory in your own 7300
In article <168@gizzmo.UUCP> mark@gizzmo.UUCP (mark hilliard) writes:
>
>I WOULDNT SUGGEST DOING THIS AS ATT HAS MODIFIED THE VARIOUS MODELS OF THE
>7300 WITH CUT RUNS, STRAPS AND OTHER NASTY STUFF TO ALTER THE WAY MEMORY 
>WORKS. THERE HAVE BEEN HORROR STORIES ABOUT PEOPLE TRYING TO DO THIS MOD
>AND PAYING $2600 FOR A NEW ONE. ALSO I MUST MENTION THAT THE BOARD ARE 
>MULTI-LAYER, AND THAT UNLESS YOU HAVE BEEN TO A NASA SOLDERING SCHOOL THAT
>YOU CAN REALLY MESS UP THE BOARDS WITHOUT EVEN KNOWING SO. CALL AMPERFAX
>AND THEY WILL GIVE YOU LOTS OF DOCUMENTATED CASES WITH PHONE NUMBERS.

Sorry Mark, but I disagree with your statement! I too wanted to upgrade the
memory in my 7300 and and called Amperfax to ask how difficult it is. They
tried to scare me off with the same arguments that you've mentioned above.
Then, I went to a group of veteran hardware guys here at Bell Labs and asked 
them what their opinion was. They said that you do have to be careful on
multilayer boards, but it's no more difficult than desoldering on a single
layer board. As far as strap changes and cut runs, I can't speak for all
versions of the motherboard, but for mine (p3...p5) the change is simply a
jumper change. I even have a copy of the instructions on how to do this that
appears in a document published by Convergent themselves! My conclusion is that
Amperfax is trying to get buisness (which is a valid thing for them to do)
and so try and discourage folks from doing this. For me, their prices are too
high for something I can do myself.

Now, if your wondering how I can say all this, it's because I've recently taken
a 0.5MB expansion board and ripped all the 64K chips out, installed sockets,
and populated them with 256K chips. This took about 4 days, because I was so
worried I'd screw up something, now I feel I could have done it in 2 easy
days, or one work-hard day. After I did the hardware, I spent almost 3 weeks
playing phone tag with the jerks at Convergent trying to figure out the jumper
configuration (It's not the same on the expansion board as it is on the
motherboard). When they did answer me, they gave me the wrong answer. Finally
a very smart guy in AT&T figured it out and told me how it works. It takes 3
jumper wire changes... thats it! I now have a 2MB expansion memory board
working in my unix-pc.

I will be going after the motherboard sometime soon as my next project. If
*ANYBODY* wants to do this, I will gladly send instructions/recommendations,
etc. I would advise that you DON NOT take what you hear from amperfax as bible,
and by the same token don't take what I say as bible either. Find a hardware
guy that's knows his stuff and is familiar with you and ask his advice. I'll
bet that you'll end up giving it a try too!

I will be posting a detailed article in unix-pc.general as to how I did this.
If you don't subscribe to this newsgroup, send me mail and I will gladly send
you a copy!

Craig Votava
AT&T Bell Labs, Naperville IL
IH 4G-324 x2542
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