[TUHS] A PDP-10 used for UNIX just after the PDP-7?

[Noel Chiappa via TUHS]

    > From: Thalia Archibald

    > in Thompson's 1989 interview with Mahoney, he mentions that "Before the
    > 11/45 was available we bought a PDP-11 that had PDP-10 memory
    > management, KS-1, it was a one of a kind machine".

In trying to find out more about the KS11:

  https://gunkies.org/wiki/KS11_Memory_Protection_and_Relocation_option

I queried Ken, and he was nice enough to reply, and explain to me that it
operated like the memory management hardware on the KA10 model of the PDP-10.

I think that's how the 'PDP-10' confusion started.


    > Does anyone know anything about this strange PDP-11 + KS-1?

The KS11 was the very first hardware memory mangement available for the
PDP-11. So, it was either that - or a bare macine (-11/20) with _no_ memory
mangement.

Bob Supnik told us a bit about the KS-11: "The KS11 created a PDP-10 (KA)
style memory management system for the 11/20: that is, high-segment
(instructions, in theory, and shareable, in theory) and low-segment (data)."

No documentation on the KS11 has ever been located. There is KS11 emulation
included in Bob's MIMIC PDP-11 simulator; in theory someone energetic could
dig into that, and work out the details of how it works. More here:

  https://gunkies.org/wiki/Talk:KS11_Memory_Protection_and_Relocation_option

if anyone is interested. MIMIC was written long ago (the header says "March
31, 1971"); it's in PDP-10 assembler (it long pre-dates SIMH), so it wouldn't
be trivial.

There was also support for the KS11 in UNIX V2, from which it would be easier
to produce a programming manual for the thing. Alas, that version of UNIX has
been lost (although a bit about how the KS11 worked can be deduced from the
V2 manual, which is extant).


    > What was the model of PDP-11 first used for UNIX?

The PDP-11/20. Dennis' "The Evolution of the Unix Time-sharing System":

  https://www.nokia.com/bell-labs/about/dennis-m-ritchie/hist.html

indicates that they got it _very_ early in the life of the -11: "the PDP-11
was so new a product that no disk was available until December". A later
comment there ("a single .5 MB disk") indicates that they probably got an
RF11:

  https://gunkies.org/wiki/RF11_disk_controller

Not sure why they didn't get an RC11.

    Noel