Comment Late 1989, on a VAXstation II/GPX (Score 1) 204
Late 1989, on a VAXstation II/GPX running VMS 5.0. Not exactly a desktop workstation, it was a desk-side box as big as a 2-drawer file cabinet. That newfangled DECWindows came out and killed off the old VMS GUI "VWS". Right about that same time the VAXstation 3100 came out, a true desktop VAX workstation...
The early versions ran a "desktop" called "XUI", which was replaced with Motif in 1991.
Another commenter wrote that the performance has not improved that much since the early 90s. My current desktop Linux box has the equivalent CPU horsepower of 10,000 VAXstation 3100s, but it boots to the login window only about twice as fast. Progress?