> I have just received an SGI Indigo - (R4400 processor).  I've never 
> dealt with this machine before and I am totally unfamiliar with bus 
> specs and other issues.

Plan-9 source code tree has indigo4k/ directory as well as indigo3k/,
which are valuable source of the machine internals. 

Tohru Nishimura
Nara Institute of Science and Technology