I need to write supervisor-software for handling register-window
	traps (and context-switches, and interrupts... ;) ) and SUN's own
	books (including the SPARCv9 manual from SPARC International) are
	brief on the subject, to say the least.

Register windows and traps on SPARC v9 are pretty much
a black art.  The basics are in the Sun manuals, but the
corner cases make you pull your hair out.  All that stuff
is in src/sys/arch/sparc64/sparc64/locore.s and is designed
primarily for maintainability, so although it's probably
less efficient than it could be, it is hopefully more legible.

Eduardo