Open Sourced processor

I was pleasantly surprised to see that SUN has opensourced the architecture of
their UltraSparc T1 processor.
http://opensparc-t1.sunsource.net/ contains a lot of stuff related to the
processor. The docs are very good. Chip architecture is very useful for s/w
programmers, since the h/w plays an important role in the way kernel behaves,
so essentially it helps them understand why things work in a certain way on one
processor and otherwise on another processor.