I was living with a Nextstation running along my newer machines until
quite recently.

So far, the authentication is the same, though we intend to change
that in the not too distant future.  Ditto the 9 protocol.

The cpu command uses a different protocol than the old systems.  You
can recompile the old cpu command on the new systems (call it ocpu
or something) and use it to talk to the old systems.  The new cpu
command uses a different port so they can both exist on the
same machine though you will have to edit ocpu.c to change the service
name to something else.

Graphics are radicly different so you can't cpu from one to the other
and use any of the graphic commands like rio, sam, etc.

Sam -r will work though since the protocol between the halves is
unchanged.

Of course, you could just port the new system to the Sun hardware.
It shouldn't be that difficult with both the new and old in hand.
We didn't because we don't really use suns, most of our old processors
are mips.