This looks very much like the problem I had.
You have your BBA hooked up to a hub, right?

In my case, the problem is that the dreamcast BBA handles
collision detection *extremely* poorely. This combined with
the incredibly stupid backoff routines in NFS makes it
impossible to use a rsize over 1024 bytes in some cases.

There are two solutions to the problem: Use a kernel
compiled with RSIZE set to 1024. If you can't find one
or make one I can give you the one Marcus Comstedt compiled
for me. 

The other solution is to make sure that collisions never happens:
Either by hooking up your BBA to a full-duplex-capable switch, or
hook up your BBA directly to a computer/network card/router with
a crossed ethernet cable.  This solution also has the advantage that
you can get around 500Kb/s through your BBA instead of 50Kb/s
with RSIZE=1024..

        /Fredrik Hubinette (buying a switch real soon now)


Nathan Mahon <nate@aftershock.blackhat.net> writes:

> Okay.... its on ftp.netbsd.org and i'm downloading it now.
> I had previously set up the files i mentioned, and when i boot it with
> everything, it seems to hang/stop its boot after the following lines:
> 
> <kernelstuff>
> nfs_boot: Trying DHCP/BOOTP...
> nfs_boot: Timeout...
> nfs_boot: DHCP server: 10.5.5.203
> nfs_boot: my_addr: 10.5.5.129
> nfs_boot: my_mask: 255.255.255.0
> root on 10.5.5.203:/usr/home/vae/dc-fs
> root file system type: nfs
> 
> 
> <hang>
> 
> 
> any clues?
> will switching to the 20010227 set work?
> 
> n8
> 
> PS: using IPSlave and a NetBSD server...
> 
> 
> 
> 
> On Tue, 5 Jun 2001, scav wrote:
> 
> > It seems my first response went directly to Jared by mistake:
> > 
> > Strangely enough, a snapshot can be found here at
> > /pub/NetBSD/arch/sh3/snapshot/20010227-dreamcast-elf-test on the ftp
> > (ftp.se.netbsd.org at least, but should be the same.)
> > 
> > --scav
> > 
> > > I was wondering if there was an alternate location to get up-to-date
> > > snapshots from, as the location referred on netbsd.org/Ports/dreamcast
> > > (ftp://ftp.netbsd.org/pub/NetBSD/arch/dreamcast/snapshot/) contains no
> > files.
> > >
> > > Thanks for your help.
> > >
> > > -J
> > >
> > >
> >