I eventually succeeded to copy the tar files over from 
ftp://ftp.netbsd.org/pub/NetBSD/arch/pmax/binary/, and to install them in 
partitions that are intended to eventually become the root and /usr 
partition of the system. In order to boot from that new root system, I'd 
need a kernel. As a first guess, I copied /netbsd from Jonathan's 
miniroot over, but the machine hung after displaying the line

init: copying out path `/sbin/init' 11

(when booting from the miniroot, the next line displayed is
<date> init: /etc/spwd.db: No such file or directory).

Is there any working kernel with device support similar to the one in the 
miniroot available anywhere which I could pick up? If not, where should I 
pick up sources for a new kernel build, and how should I proceed?

Helge