Ian Bicking: the old part of his blog

Comment

I can almost guarantee that the process switching overhead in Windows is far less than the overhead that you get with the GIL... because guess what, two chunks of python code can NEVER EVER RUN AT THE SAME TIME with Python threads! :) It's only carefully written C code that can explicitly allow ONE python thread to run concurrently while it's doing something way outside of the Python domain.

That said, I don't use Windows anymore, so I can't do a benchmark, but I think you are blowing the win32 process switching overhead out of proportion.
Comment on Initial thoughts on Prothon
by Bob Ippolito