Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!ucsd!ogicse!zephyr.ens.tek.com!gvgpsa!gold!grege
From: grege@gold.GVG.TEK.COM (Greg Ebert)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: PC (XT) keyboard & XT/286 m/b
Message-ID: <1342@gold.GVG.TEK.COM>
Date: 24 Aug 90 21:18:01 GMT
References: <25345.26d502c6@kuhub.cc.ukans.edu>
Organization: Grass Valley Group, Grass Valley, CA
Lines: 34

In article <25345.26d502c6@kuhub.cc.ukans.edu> michal@kuhub.cc.ukans.edu (Merlin The Magician) writes:
> Is there any way to get an 84-Key Keyboard to work with an AT
>Motherbaord ? 
>
> IBM local dealer says the two keyboards use a diffrent scan and you
>CANNOT use an XT (PC) keyboard on an AT m/b. But then the rep also
>flatly denied the existance of an IBM XT/286. 
> 

The AT and XT (PC) keyboards DO use different scan codes. At power-up, a
kludgy protocol between the keyboard and an AT system tells the keyboard
controller in the AT what kind of keyboard is present. My undrestanding is
that an XT (PC) system cannot understand a regular AT style keyboard.

Finally, to add more confusion, I think there is an auto-switch keyboard
which sets itself for PC or AT operation depending upon what kind of system
it's plugged into, while at the same time the system tries to figure out
what kind of keyboard is present. Sounds like a chicken/egg sydrome at 
power-up!

You CAN put a PC keyboard on an AT, and it does work. I suspect that your
system does not have the same kind of keyboard controller as a typical
AT system. Believe it or not, the keyboard controller is the most
complicated component in an AT system, and accounts for a large number
of incompatibilities. It's possible that your keyboard controller does not
have the software to support both type of keyboards. I know a guy who has
done oodles of keyboard controller software [hi Bob Hale!], and is
frustrated by the tiny amount of ROM in the 8742. When you think about it,
there's really no dire urgency to support PC keyboards on an AT anyway.

- - - - - - - - -
Here's a true keyboard-controller saga: The company I used to work for
found a new vendor for power supplies. They didn't work. Solution: a
software change in the keyboard controller. No B.S. !!