>I can imagine adding a ROM that would map into the 
>Qbus memory address space and
>provide a boot program. On a PDP-11 this would 
>eat up precious RAM. I don't
>know if/how the Qbus memory address space is 
>mapped into the VAX address space
>or if it is executable, etc.

Most, if not all, Q-bus MicroVAXen support
  >>> BOOT PRA0:
which boots from a PROM. The prom is found by 
scanning Qbus memory (IIRC) looking for an
appropriate signature and then diving in.

I don't know whether I have enough details
to hand to allow you to do this in V2 :-)
I expect the exact details may be in EK-KA630-UG
(which I don't have ...), they may also be
in the corresponding EK-KA655-TM (which I do
have but cannot look at until tonight).

Antonio