> I am pretty new to the VAX hardware, but I am pretty good with Linux
> and BSD (I run a OpenBSD machine for my main server) and I have got my
> hands on a VAXStation 3100 M38, which is alien hardware to me. I have
> set it up so I can talk to it via serial port, however it gives me
> some weird bootloader 'KA42B' I don't even understand (references?).
> Nonetheless I was hopeing someone would be able to help me install
> NetBSD on it via the floppy drive it has. If I figure out how to boot
> it and then do an install across NFS or just FTP straight from the net
> I should be right, right?

At least this worked for me a couple of years back (using local monitor
and keyboard, not serial console).
I remeber however that it was quite difficult top find a working floppy
image. I think newer releases no longer feature an image that fits on a
floppy disk, although the docs still claim so.
As an alternative, you might prepare a suitable SCSI disk elsewhere
(preferably some other NetBSD system), extract the essential Vax binary
tarfiles and put the correct bootloader onto it. That should boot.
This is how I recently installed NetBSD 2.0 to my vax, using a DECstation
to prepare the SCSI disk.

-- 
Georg Schwarz    http://home.pages.de/~schwarz/
 georg.schwarz@freenet.de  +49 178 8545053