[chasil]

The original kernel from which Windows evolved was written in assembler by Dave Cutler for the VAX architecture. After his DECWest team was hired by Microsoft, they reimplemented it in C. The MIPS architecture was the first fully complete port, I believe.

This is documented in Zachary's Showstoppers book:

https://www.flyingpigbooks.com/book/9780759285781

It appears that performance and architecture improvements are very hard to get accepted (and the kernel suffers for it):

https://blog.zorinaq.com/i-contribute-to-the-windows-kernel-...

It is a great piece of engineering, but it is likely for a developer that is more comfortable making small changes within the hierarchy than for any revolutionary ideas (unfortunately).

If Cutler hadn't found his way to Microsoft, then they probably would have ended up on a BSD kernel, as Apple did. As it was, Microsoft sold their Xenix business around the time of Cutler's arrival.