Problem Booting System 5 on 11/70

[Henry Spencer]

> He has an 11/70 with a western peripherals controller which emulates an
> rm05. When he attempts to boot he gets a trap 0. This controller-disk
> combination works perfectly using RST/S but somehow system 5 seems to
> have problems....

Bell/AT&T RP/RM drivers are notorious for assuming that, if they're on
a 70, the controller must be on the Massbus (loose terminology here,
but it's what people understand).  If your Western Peripherals controller
is a Unibus controller, that's almost certainly where the problem is.
The difference is in how >16-bit addresses are handled; the "Massbus"
controllers can directly address 22 bits of memory, whereas the Unibus
controllers need help from the Unibus map.

The underlying problem is that AT&T buys only certain combinations of
peripherals for internal use, and doesn't test on other combinations.
(At least, that's the way it used to be.)  Evidently DEC is more paranoid
about varying configurations (hence RSTS works).  Berklix will probably
handle this correctly, since Berkeley is/was heavily into non-Dec and
hence often non-Massbus controllers.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry