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

[Warner Losh via TUHS]

On Fri, Jan 16, 2026 at 12:12 AM Thalia Archibald via TUHS <tuhs at tuhs.org>
wrote:

> On Jan 15, 2026, at 23:57, Ken Thompson wrote:
> > after the pdp-7, unix was ported to more
> > stock pdp-9 and pdp15 (both pdp7 upgrades)
> >
> > no pdp-10 at bell labs.
>
> Hi Ken,
>
> So the "PDP-10" that Mahoney refers to is the PDP-11 with KS-1 memory
> management? Seems like a strange machine.
>
> And did you only ever use the one PDP-7 from the graphics group, and the
> other
> PDP-9s and 15s were used by other groups?  Warner Losh writes that the
> PDP-7
> UNIX “Total install base was 4 (1 pdp-7, 2 pdp-9 and 1 pdp-15)”.
>
> https://papers.freebsd.org/2020/fosdem/losh-hidden_early_history_of_unix/


I wrote that because I found references, I think in the 0-edition manuals,
that had those
numbers. I got the impression from somewhere, and I can't quite find it
this morning, that
those machines were 'cast off' that the department used on an interim basis
until they could
get a pdp-11. But the evidence was thin at the time, and I included it
because it was more
than 0, which was a surprise to me.

Warner