Contrary to popular opinion, it is possible to directly
boot NetBSD on an OFW3/OFW4 Macintosh without having MacOS
on the disk.

The primary difficulty is to get OFW to load ofwboot.elf or
ofwboot.xcf off the disk.  This has been mostly been done to
date from MacOS but I reasoned that if OFW can load ofwboot
from an ISO9660 on a CD, it should be able to same with a HD.
And it does.

The first thing is to create a small ISO9660 file with only
ofwboot.xcf (or ofwboot.elf - your choice).

	mkisofs -r -apple -o boot.iso ofwboot.elf

Then you need to put that on the disk.  But you have to skip
the first 16K of the disk as to not overwrite NetBSD disklabel
you may put there.

	dd if=boot.iso of=/dev/wdXc skip=32 seek=32

Once it's there, you can then disklabel the disk.  Remember to
allocate space of the beginning of disk for the ISO9960 file
system you put there (say 256KB).  Parition the rest of the
disk as you like.  Note that the 'a' parition will start some
place after the ISO9660 and it must not overlap it (or start at
0).

setenv boot-command boot
setenv boot-device hd:OFWBOOT.ELF;1
reset-all

Note that I did this on a head-less Mac G4 (console is on the
serial potr that the modem connects to) so I don't know if OFW
is correctly initializing the display.
--
Matt Thomas               Internet:   matt@3am-software.com
3am Software Foundry      WWW URL:    http://www.3am-software.com/bio/matt/
Cupertino, CA             Disclaimer: I avow all knowledge of this message