Amusingly the hardware between the 9000 and 3000 line are the same. The 9000's were
marketed with HP/UX.
The 3000's ran MPE (or as we called it Mighty Poor Excuse). I had an HP/UX machine
back when I was consulting
with Unipress back in 87 or so (and then we did a lot with them in my later job when the
newer systems came out).
But I'm trying to remember a pre-X windowing system and can't think of it. The
later HP/UX had an their own proprietary
Motif-based window manager.