>What can I do? Is there a bootblock that can boot the new kernel on 
>my DECstation 2100?


To the very best of my knowledge, the only NetBSD bootblocks that work
on Decstation 3100s and Decstation 2100s are on Gregorio.Stanford.EDU.
These should work on [23]100s, 5k/200s, and 5k/{2x,1xx,240}.

Other bootblocks -- e.g., built from the NetBSD-current source -- only
work on machines with the `new-style' PROM and PROM callback: that is,
Decstation 5k/{2x,1xx,240}s.

Very early NetBSD/pmax bootblocks, from nearly a year ago, worked
only on 3100s (probably 2100s) and 5000/200s.  I'd be astonished
if any of these bootblocks are floating around the net.

I've just commited the (simpler) bootblock changes  to -current;
the remainder of the changes will take a while.