We're talking about 1982, not 'mid to late nineties'. None of those chips even existed. Silicon Graphics Unix was running on 680x0 based series 1000 machines (and wasn't called IRIX yet). HP/UX was running on 680x0 based HP9000 series. AIX was a couple of years away and would first run on the RT/PC development of the 801 project, not on POWER. In 1982-ish IBM did have a Unix machine tho...the 9000 series, which was a 68000 running Xenix. DEC hadn't started PRISM, much less ALPHA then...it's Unix was Ultrix on VAX and PDP-11.
No, there weren't. There were the few you mentioned, and a dozen or two others. I worked with most of them. The point was that in the early 80s, there were a far larger number. The only real similarity was that like the '80s were the days of mc68k and Unisoft, the majority of the 90s Unix vendors were x86 and System V, all from the same code base.
