[chasil]

Bear in mind that Microsoft was the largest commercial UNIX vendor in licensing XENIX for the TRS-80 Model 2 alone. From this experience, they had significant knowledge of 32-bit preemptive multitasking.

That exposure allowed them to see how valuable Dave Cutler's PRISM team would be in a total redesign in melding VMS and (whatever tolerable) UNIX features into a new kernel, but focusing it upon Win32.

There were OS/2 and POSIX emulation layers also, but these were obviously second class.