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

[Charles H. Sauer via TUHS]

> 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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