problems with booting IBM RS/6000 B50

Hello all,

I got an old B50 to play with it. Installing NetBSD 5.0.2 via TFTP/NFS
works fine.

But when I want to start it from hard disk, I have no success.
In the list of boot devices I get only the ethernet adapter and
not the disks.

Unfortunately there is no INSTALL file at
ftp://ftp.netbsd.org/pub/NetBSD/NetBSD-5.0.2/ofppc/INSTALL.html
(this is the link from http://www.netbsd.org/ports/ofppc/ )

Does anybody have an idea?

Thanks a lot

Martin