[theBuckwheat]

Dave Cutler was the architect of Digital's VMS, which I think is still the best OS ever written. He was recruited away from DEC by Microsoft to head up the NT project. The first NT architecture book that I was able to purchase states it was a clean sheet design. In looking at the internals, a lot of the excellent features of VMS show through. Indeed, the null task was a signature Cutler feature.

As to the timeline where NT fits with OS/2, I cannot recall. I saw OS/2 and immediately concluded that IBM was not going to take the long view with respect to competing with Microsoft, as much as some people liked it.

As an aside, in the shop I used to work at we kept a running joke going for years: can anyone name any OS feature that Microsoft really invented. The mouse and GUI came from someone else (Xerox PARC), the spreadsheet from Dan Briklin's Visicalc. The only thing that several dozen well-connected techies could ever come up with was BOB, the "feature" that Microsoft included for only a short while in its OS.

[rzeznikj at stout]

NT 3.1 was supposed to be OS/2 3.0--IBM was to develop version 2.0.

But the collaboration between MS and IBM fell apart, with MS continuing to develop Windows. IBM continued to work on OS/2, but it never took off aside from a small and loyal niche market.

So, MS took out the OS/2 API and much of the IBM code--replacing it with the Windows API and their own code. Technically it was clean-sheetede because MS wrote a ton of new code and put it around the new NT kernel, which MS implemented.