Mark Williams' Coherent Operating System was a UNIX-like OS that ran on early PC's (Original 8086-80286 I think) and then later was ported to the 80386 with its protected mode architecture.

Unfortunately it wasn't all THAT UNIX-like, and so if you were used to working in "real" UNIX you would likely have been somewhat dissappointed.

That having been said they did a great job with the minimal resources they had at their disposal, and their support engineers were always very helpful when we called.