After trying on comp.unix.bsd.netbsd.misc without success I found 
this mailinglist which seems right for this question.

I have a DECstation 5000/20 which I am trying to boot via nfs.

After configured and started a lot of nonrunning daemons on the nfs-server 
machine I am now able to get it too boot. But not all the way.
It stops on the line:

swap on foo.bar: /swap/here

What is supposed to happen here. I guess it should init the swap or something
similar. But I have had it like that for 30 minutes without any change.
My nfs server is running Ultrix 4.4
Standard bootpd, rpc.bootparamd, rarpd, tftpd.
Swap is a null file of size 32 Mb created via 'mkfile' on a Solaris 2.4 
machine.

Is it a problem with the nfs exports? or bootparams? File permission?
Do you need any more info?

Another question related to this:

Sometimes I get ?IO: 3/tftp a.out err (-5)
in the boot monitor.
First I tought it had to do with my nfs server being to loaded
but it doesn't seem to be a good reason.

/Jonas