> 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.

It depends on how the mapping registers are set up.

I would expect the ROM would be mapped only when a certain bit is poked
in some register.  On a non-discrete-logic board, I would also expect
there to be a base register which says where the ROM contents appears,
but that might be too much for a discrete-logic board.  (Fortunately,
PIC code is relatively easy to do on the VAX.)

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