[ ... NetBSD/pmax can not talk with le0 ... ]
>>> # ping 10.1.3.1
>>> PING TO 10.1.3.1 (10.1.3.1): 56 data bytes
>>> le0: device timeout
>> 
>> It's very interesting.  Although this might sound a dumbest question,
>> is the network connection 100% ok?
>
> The network definately works ok. I can boot (or at least load and crash)
> any of the ecoff kernels and I can boot DECStation Linux using TFTP and
> NFS root and telnet into the box and play around.. 

'Key, I assume you are using 'MAU unit' to adapt DECstation AUI port
to 10baseT or 10base2.  If you are familar with tcpdump(8) or similar
network traffic analysing tool, is it possible for you whether to
verify any outgoing ethernet frames after NetBSD/pmax boots itself and
the 'le0' network interface is initialized?

BTW, you can run full-scale (not-short-and-quick) self diagnostic test
with 'test' command for '>>' PROM prompt.

Tohru Nishimura
Nara Institute of Science and Technology