[TUHS] Is there a good, even definitive, list of reimplementations of the Unix kernel? What would good cut-off criteria be?

[Clem Cole via TUHS]

Charlie,

I’ll make a small WAG having been part of the later history. I believe the
UCLA ( original ) SOSP Locus paper was based on PDP-11/70s and predated
BSD3 [which was the original Vax release].  It is likely that UCLA had the
original BSD for 6th edition and possibly 2BSD which was for both V6 and
V7.

When LCC was created was post 4BSD and the IBM AIX 370 and PS/2 work for
what become TCF  was based on 4.1. I suspect Bruce’s comment was based on
the later work.

Clem


Sent from a handheld expect more typos than usual


On Sat, Apr 18, 2026 at 11:49 PM Charles H. Sauer via TUHS <tuhs at tuhs.org>
wrote:

>
> > On Apr 18, 2026, at 9:52 PM, Bakul Shah via TUHS <tuhs at tuhs.org> wrote:
> >
> > I believe Sol later merged into Chorus was a reimplementation in Pascal.
> I think this was a microkernel based system...
> > I believe Locus distributed OS designed at UCLA was also Unix
> compatible. I guess you can add Xinu as well as Amoeba to the list.
>
> I intentionally never looked at Locus source, but had much interaction
> with Gerry Popek and Bruce Walker while I was at IBM and they were working
> with IBM. I have a memory of Bruce telling me they started with 4.1BSD, but
> I question that memory. Just glancing at their book (
> https://www.penguinrandomhouse.com/books/655167/the-locus-distributed-system-architecture-by-gerald-j-popek/),
> the only cited Unix reference I see is the 1978 Ritchie/Thompson BSTJ
> paper. Section 1.5 Unix Compatibility of their book says “For virtually all
> applications code, the LOCUS system can provide complete compatibility, at
> the object code level, with both Berkeley Unix and System V, …” I suspect
> that the first Locus prototypes were based on BSD earlier than 4.1.
>
> Charlie
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