After looking at the code, it appears that if the open fails in
if_prom.c:prom_init, it will always display 7 (it's calling a
function that returns an int and stuffing that into a 64-bit
quantity.  If the open fails, prom_open returns -1 which will
fill the prom_return_t with 1's.  The value printed out by
prom_init is a 3-bit bitfield...

I was able to find a place to build my own bootblocks and poke
at this a little more.  The open is return a status of 4, which
(according to some information from David Seifert) means that
the device was not found.  The device name being passed is:

	BOOTP 0 7 0 0 0 2 CORE-IO

(devlen is 25, devlen + 1 is passed in to the prom_dispatch
 call).

Unless anyone has any better ideas, we're going to skip the
netboot and start playing with SCSI disks and disk images.
*sigh*

Thanks again for the help so far.

-allen

-- 
                    Allen Briggs - briggs@ninthwonder.com