Why is there no GIL in the Java Virtual Machine? Why does Python need one so bad?

Question

I\'m hoping someone can provide some insight as to what\'s fundamentally different about the Java Virtual Machine that allows it to implement threads nicely without the need

Answer 1

There is a comment down below in this blog post http://www.grouplens.org/node/244 that hints at the reason why it was so easy dispense with a GIL for IronPython or Jython, it is that CPython uses reference counting whereas the other 2 VMs have garbage collectors.

The exact mechanics of why this is so I don't get, but it does sounds like a plausible reason.