There is a very old patent, 1982, that Compaq owns
that they claim covers
Exactly how long do patents last these days? Did it not used to be 17 years
(max - assuming the renewal fees were paid)? If so, has it not expired?
The IBM patent server should be able to track it down (given a few more details)
and (IIRC) it will tell you if it is still in force.
Antonio