In message <20040407201617.498BC7B44@berkshire.research.att.com>Steve Bellovin writes

>Does anyone have any experience using Thinkpads (and in particular, R
>-series Thinkpads) with IBM port replicators and XFree86?  I tried it 
>once, with a borrowed replicator; it didn't work, but I never pursued 
>the question of why, and I had some indications it could have been the 
>port replicator itself.  The intended application would be using 
>external keyboard, mouse, display, and probably Ethernet, under 2.0.

I suppose an 600E/600X is too old to be relevant?  Those worked for me
with the lockdown "base stations" (no ethernet).
(No external keyboard, though; only mouse, just as with the laptop itself).