Ah yes, IRIX. My biggest recollection of it was being annoyed that they had a bug in updating the utmp file correctly, so that it would sometimes leave users in it that were no longer logged in the system. I wrote a quick and dirty cron job hack that would compare the utmp to the wtmp entries once a minute and delete any stale users it found, and I posted it to usenet for anybody else annoyed by the issue. I was surprised a while later to see that rather than fixing the bug, SGI employees were recommending people install my dirty little hack.