Your win32 comment is odd. I was developing on NT during the 3.1 betas in ~1992 and we chose to go all in on multithreading. Our product launched in 1993 with t

Your win32 comment is odd. I was developing on NT during the 3.1 betas in ~1992 and we chose to go all in on multithreading. Our product launched in 1993 with the release of NT. I don't ever remember hitting an OS level thread/etc bug (fair share of footguns though). More than a year later we were trying to port much of the codebase to solaris and it was a nightmare. Pretty much nothing worked right so we ended up bolting on the fork/mmap abstraction on top of much of it and building our own lock wrapper. While we sorta got it working, the solaris port died for internal political reasons and the NT version took off and we never looked back. NT was designed out of the gate for heavily threaded/async workloads, that stuff wasn't bolted on like pretty much every unix clone in existence.