[pups] A bootable disk image for a PDP-11/34?

Ken Wellsch kwellsch at tampabay.rr.com
Thu Feb 1 11:37:29 AEST 2001

Carl Lowenstein wrote:
> > From wkt at henry.cs.adfa.edu.au Tue Jan 30 14:16 PST 2001
> >
> > 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.
>	...

When I looked last night at the machine assist (mch.s) for Ultrix-11/3.1
source, all I could easily find was consistent with this, contained in
the V6 start document:

    The main difference between an 11/40 and an 11/45 (or 11/70)
    system is that in the former instruction restart after a
    segmentation violation caused by overflowing a user stack
    must be handled by software, while in the latter machines
    there is hardware help.

which in more detail means, if I understand right, there is no SSR2
register in the MMU so the kernel code needs to disassemble the
instruction to backup over it for restarting as per above.

The Ultrix mch.s file has code that does this (quite a lot) and I
noticed a few cases that checked it the cputype is 34.


-- Ken

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