[pups] A bootable disk image for a PDP-11/34?
cdl at mpl.ucsd.edu
Wed Jan 31 09:30:55 AEST 2001
> From wkt at henry.cs.adfa.edu.au Tue Jan 30 14:16 PST 2001
> From: Warren Toomey <wkt at henry.cs.adfa.edu.au>
> Subject: Re: [pups] A bootable disk image for a PDP-11/34?
> To: Carl Lowenstein <cdl at mpl.ucsd.edu>
> Date: Wed, 31 Jan 2001 09:13:30 +1100 (EST)
> CC: pups at minnie.cs.adfa.edu.au
> MIME-Version: 1.0
> Content-Transfer-Encoding: 7bit
> In article by Carl Lowenstein:
> > Just from the historical point of view, note that the first major
> > file on a genuine 6th Edition distribution tape _is_ a bootable
> > RK05 image. Something like 4000 blocks.
> > carl
> Yes, but it doesn't boot on an 11/34 :(
> That's the problem.
Why, said he wonderingly. Is the 11/34 one of those machines that does
not have a directly addressable PSW at 177776 so it must be done with
MPTS and MFPS instructions? Thats all I can think of immediately.
Pulling out my handy PDP-11 architecture handbook, I find this to be so.
There are some other differences between 11/34 and 11/40-45 but this
one would be a real show-stopper.
The modifications to 6th Ed. Unix to take care of this would be
concentrated in the save/raise/lower processor priority routines. Just
offhand I don't think one could make a zero-length binary patch that
would work on the 11/34 and remain 11/40-45 compatible.
I guess I will look at locore.s tonight when I get home. That must
be the place where such things happen.
I wonder what the RT-11 guys did when they had the same problem. I
seem to remember something involving creative use of stack pushes and
RTI instructions to set the processor priority.
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