I learned the hard way not to open the gull wing doors on the thing while someone was using it.
When HP/Apollo merged and they formally pulled the plug on Domain, I was over at the FAA and they showed me the “latest” computer they got in that was running a system to show where all the planes in the airspace system were (think of
FlightAware.COM, this was a first stab at pulling that data from the ATC computers). It was a DN4000? running domain. Always using the latest stuff at the FAA.