From Showstopper! The Breakneck Race to Create Windows NT and the Next Generation at Microsoft by Zachary, we learn that Microsoft hired Cutler in October of 19

From Showstopper! The Breakneck Race to Create Windows NT and the Next Generation at Microsoft by Zachary, we learn that Microsoft hired Cutler in October of 1988. By this time, Microsoft had already maintained a 32-bit kernel with a flat memory model as Xenix. They disposed of it because AT&T was entering the commercial UNIX market and Microsoft would be at a distinct disadvantage. This means that Cutler had been expounding on his grand kernel plans for two years prior to the 32-bit OS/2 from 1990, and staff at Microsoft could very well grasp the significance. Chapter 4 of Zachary, Blind Alley, claims that the NT development kernel booted on an i860 PC in July of 1989. This being the case, the knives must have been out for OS/2 for some time. https://en.wikipedia.org/wiki/Dave_Cutler https://en.wikipedia.org/wiki/Dave_Cutler