I am using a SUN UltraSparc-I workstation for a low-level project
and would be most grateful if anyone could share some enlightenment.

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.

Assuming port-sparc64 is as well designed as NetBSD in general, I got the
1.5 release sources[0] (which I needed anyway for my own port-sparcs) and
am right now in the process of figuring out where to find the
architecture-dependent sources for register-windows and traps. It would be
great if someone could point me in the right direction, but most
importantly, outline how register-windows are efficiently managed (I can
read the source, but an overview of how it works would be invaluable to
understanding it).

Just pointers to this kind of information would be great.

[0] The project doesn't actually involve NetBSD other than as a point of
    reference.

TIA,
 Anders Lindgren