netbsd-ports doesn't get much traffic, so here's my contribution :-)

So how do you decide whether or not to keep the prom mapped in beyond
the boot stage?
 
For example, it appears the alpha does and i386 doesn't. For the
i386, the bios is 16 bit code and non-reentrant so I can see that
being the main reason not to. It appears powerpc does because it
is currently leveraging that in lieu of device drivers. I thought
I recently read that mapping in the prom on the alpha took up 2MB
of real memory. What main value do prom routines provide beyond
booting? Cache management? just convenient generic code between 
different models of the same hardware?
 
I would think mvme68k has pretty extensive PROM support, does that
port use it beyond the boot stage?  

I would also be interested if someone could comment on the sparc and 
sun3 ports use of the prom.

Jason