> Consider/compare Sun: there's lots of info on SPARC-the-processor.  But
> that doesn't mean you can find out how a Sun Ultra works in enough
> detail to do an OS port to it, even though it's a SPARC machine.

The Ultra Architecture manual has all of the information you need to
do a complete OS port.  Linux for example, has been ported to the
Ultra now.  And there are even two ports of it: the 32 bit port and the
64-bit port. 

Miguel.