When I attempt to boot diskless I do receive 
the message:

WARNING: boot program didn't supply boot device.
Please update your boot program.

Does this belong to the BIOS configuration(hp300)
or is there somewere a parameter that can be adjusted?

I do find a /usr/src/sys/boot directory but it is empty.

I also attempted to compile the kernel with 'config netbsd root on nfs 
swap on nfs' but this seemed to be a wrong idea.

Manpage boot(8) is missing in my NetBSD 1.2 distribution for hp300.