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

[Thalia Archibald via TUHS]

In Mahoney's oral history, he writes that after the PDP-7, "The file system was
then put on a PDP-10". And 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".

Are these the same system? I've never seen any other references to a PDP-10 used
in early UNIX development, only that their request for a 10 was denied. Does
anyone know anything about this strange PDP-11 + KS-1?

What was the model of PDP-11 first used for UNIX? What hardware was sold by the
UNIX group to the patent department? I presume it was an 11, since the 7 was
never their property.

Mahoney's words:

    When Thompson realized that the PDP-7 was not powerful enough to implement a
    file system that could offer some of the advantages of Multics he initially
    programmed a bare-bones file system. The file system was then put on a
    PDP-10. Using this enhanced capability, Thompson and the others slowly added
    tools that helped them monitor what the file system was doing. Thompson
    devoted a month apiece to the shell, editor, assembler, and other software
    tools. When asked when he realized that a new operating system was being
    born, Thompson replied,

https://dspinellis.github.io/oral-history-of-unix/frs122/unixhist/finalhis.htm

My summarization of the relevant paragraphs of Thompson's 1989 interview:

    After the PDP-7 was at the end of its life, they needed a new machine, so
    they proposed to buy a PDP-11 model that was about to be announced. The
    proposal was rejected, but the psychology research department decided to buy
    it and give it to them. They placed the new PDP-11 in Osanna's office next
    to the PDP-7 and wrote cross tools. They wrote a PDP-11 assembler on the 7
    in B and ran the paper tape across the floor to the 11. For its first month,
    the 11 was without a disk, so they had a fake in-memory filesystem. Once it
    was delivered, they got UNIX running on it in about a week and, at this
    point, the topology of the directory structure was rather fixed.
    
    When the patent department was about to buy AstroText, a horrific and
    expensive typesetting package, they instead produced a version of
    nroff/troff for their specific formatting needs. They also talked the patent
    department into buying their system, i.e., the physical hardware, and moving
    it out. With that money, they bought an 11/45. Before the 11/45 was
    available, they bought a PDP-11 that had PDP-10 memory management, KS-1, a
    one-of-a-kind machine. This was the first time they were using the machine
    at the same time for program development as typists.

https://dspinellis.github.io/oral-history-of-unix/mike/transcripts/thompson.htm

Thalia