I don't know if it's true or not, but I've long blamed Microsoft for killing SGI (Silicon Graphics Inc).

MS worked with SGI on a project known as Fahrenheit - to unify Direct3D and OpenGL:

https://en.wikipedia.org/wiki/Fahrenheit_(graphics_API)

...well, we all know what happened - but I've often thought that Microsoft hastened their demise.

Somewhere in there, of course, was also the whole SGI moving away from IRIX (SGI's unix variant) to Windows NT (IIRC, this was on the Octane platform) - there being some upset over it by the SGI community. Maybe that was part of the "last gasp"? I'm sure some here have better info about those times; I merely watched from the sidelines, because I certainly didn't have any access to SGI hardware, nor any means to purchase some myself - waaaaay out of my price range then and now.

Of course - had SGI not gone belly up, I'm not sure we'd have NVidia today...? So maybe there's a silver lining there at least?

They couldn't afford to compete with Intel on processors... they just didn't have the volumes and every generation kept getting more expensive. For Intel, it was getting relatively cheaper thanks to economies of scale since their unit volumes were exploding throughout the 90's. Also, Intel's dominance in manufacturing process kept leapfrogging their progress on the CPU architecture front.

Perhaps Digital UNIX and HP/UX but HP/Compaq was a collaborator on IA-64. I don't think I heard of SUN or IBM saying that.

Sgi is another prominent example cited elsewhere in the thread.

Indeed, it probably killed SGI.

I think there was some token POSIX compatibility in Windows NT back then. Probably for some government contracts.

It actually worked pretty nicely - if anything better back in those days when software expected to run on different unixes, before the linux monoculture of today.