Path: utzoo!attcan!uunet!decwrl!ucbvax!bloom-beacon!athena.mit.edu!jwbarrus
From: jwbarrus@athena.mit.edu (John W Barrus)
Newsgroups: comp.sys.ibm.pc.misc
Subject: Re: XT- footprint AT Motherboards
Message-ID: <1990Aug20.171803.13344@athena.mit.edu>
Date: 20 Aug 90 17:18:03 GMT
References: <27879@nigel.ee.udel.edu>
Sender: daemon@athena.mit.edu (Mr Background)
Reply-To: jwbarrus@athena.mit.edu (John W Barrus)
Organization: Massachusetts Institute of Technology
Lines: 52

I was just working with someone to install a new 386sx motherboard in their old
IBM XT.  It looked like we would just need $500 dollars worth of motherboard
(included 2M of memory) to do the trick, because I had an old AT
keyboard that he
could use.  After we got the new motherboard installed in his old
system, we
talked to tech support at the place where we got the board and they
suggested that we not use old 8-bit HD controller boards (even though
they told us that there was no problem when we were *placing* the
order.)  They said that people have had nothing but trouble with 8-bit
controllers in 386sx's because of the speedup.  (I have also heard
elsewhere that slow harddisks with 8-bit controllers can hobble
otherwise fast machinery.)

He already had a nice 16-bit VGA card and monitor (besides his original
monochrome card and monitor) and a Seagate 251-1 (28ms, 42Meg) drive
that he had added to his XT.  We could use both of those on a new
system. If we payed around $900 for a completely new system without a
hard disk or video, but with an HD/FD controller, and sold the old
system (PC/XT's are going for around $600 on the Boston Computer
Exchange) he would spend the same or less for a much better, well
integrated system.

Anyways, I know I'm rambling, but my one experience in trying to upgrade
an XT to a 386sx style machine has convinced me not to try it again,
because it isn't a good fit.  You generally need a new FD/HD controller,
a 200Watt or better power supply (which may mean a new case), and a new
keyboard.

Motherboard   $450
Keyboard      $ 75
PowerSupply   $100
FD/HD Cont    $ 75
Memory        $100
              ====
Total         $800

and you don't have enough left of your XT to sell to someone else. 
(Surely you can get more than $100 for a working XT.)

Note:
I guess I didn't figure the price of the monitor and display into the
$900 for the new machine, so that will add a little more money to the
price, or a lot more if you want VGA.

Anyways, I wouldn't try it again, because of the amount of work and
frustration.  When I upgrade, I will buy a new system and sell my old
one.  The main lesson is that you need to be aware of all the things
that need replaced when upgrading from and 8088 class machine.

John Barrus
jwbarrus@athena.mit.edu