Since my last posting to this list, I've made small steps of progress in 
that the 1.1 kernel from Arne's miniroot starts booting at least (I had 
to re-install Ultrix first in order to get rid of the Ultrix disklabel, 
it seems). The symptoms are the following now:

1) With 32 MB of memory, the boot hangs already after the line 'Starting 
   at 0x80030000'. I've seen this with the 0.9 kernel already. If I remove
   8 MB, the 0.9 kernel works fine, and the 1.1 one carries on.

2) With 24 MB, the 1.1 kernel prints the line 'tcattach: 3MIN 
   Turbochannel' twice and hangs then.

Any idea what goes wrong, and how to fix it?

I'm using a 5000/120 with 2 MB SIMMS, which fill either 2x6 of the 2x8 
slots (for the 24 MB configuration) or all slots (for the 32 MB one).

Helge