Looking at the Wiki page, the Sun Blade 100 dates from 2000 to 2006, PCs from that era were reasonably powerful by most modern standards, just lacked 1) a lot of cores, 2) shitloads of memory. For most uses, they are still great for daily tasks, and at a university, he probably had access to some remote supercomputer if he really needed it :P

My ageist perspective here is that what you're describing takes a bit of work and most "older" profs can't be arsed to do that work, so the simplest explanation is that he just still runs an old computer :)