My office mates were reminiscing about this recently. They're a bunch of IBM mainframe geeks and were lamenting IBM's decision to go with the 8086 running a CP/M clone, rather than the S/370-on-a-chip running MVS. Would this have been OS/2 ten years early? It probably would have had the same cost problems as the real-world Unix-based architectures did, but it's fun to imagine worlds where powerful software tech won in the market. (It could still happen.)