Well, I just made a "vax780" specific kernel config file and built
a kernel and booted it with simh (vax780)
# ps axl
ps: warning: /var/run/dev.db: No such file or directory
UID PID PPID CPU PRI NI VSZ RSS WCHAN STAT TT TIME COMMAND
0 0 0 0 103 0 0 296 schedule DKl ?? 0:00.01 [system]
0 1 0 0 63 0 28 352 wait Is ?? 0:01.09 init -s
0 2 1 0 63 0 188 728 wait Ss ?? 0:-1.31 -sh
0 5 2 1024 21 0 72 508 - R+ ?? 0:00.05 ps -axl
# uname -a
NetBSD vax 5.0_BETA NetBSD 5.0_BETA (VAX780) #0: Wed Jan 7
14:41:23 EST 2009 brad@mwave:/files1/netbsd/NetBSD-5_beta/root/obj/
files1/netbsd/NetBSD-5_beta/root/src/sys/arch/vax/compile/VAX780 vax