In the end it was GNU/Linux under Intel the one which ate propietary Unix workstations. By late 90's (and even more in early 00's) MESA was getting good
enough to surpass Irix machines.
Maybe at the bottom end. I was using SGI Onyx 2's in the post-production world all the way up to 2005. You couldn't run Inferno on a linux box running Mesa.
I’m not saying that SGI weren’t involved with DRI, but Inferno cost about £1,000,000 a seat, and the suite was booked out at £1000 per hour. There really isn’t any comparison between a PC running DRI graphics and an Onyx 2 with 128 CPUs and 256 GB (yes, GB, even then) of RAM, running (programmable GPU) InfiniteReality2 graphics.