By Unix-11, it seems we mean an early Unix for a PDP-11 that lacks an MMU… I still don’t have an answer but I’ve found a number of interesting links:
The earliest mention of Unix-11 I found is in The UNIX Time-Sharing System by Ritchie from 1970 or so:
There are two versions of UNIX. The first, which has been in existence about a year, runs on the PDP-7 and -9 computers; a more modern version, a few months old, uses the PDP-11. This document describes UNIX-11…
UNIX-7 also has a version of the compiler writing language TMGL contributed by M. D. McIlroy, and besides its own assembler, there is a PDP-11 assembler which was used to write UNIX-11.
In the later and prettier paper from 1974, The UNIX TimeSharing System we find there are now three versions of UNIX, and
The second version ran on the unprotected PDP-11/20 computer.
Here’s a dissertation, by John Gilmour, aiming to run this version in emulation, in 2018:
The Restoration of UNIX: Emulating UNIX version 1.0 on a 16-
bit DEC PDP 11/20
In 1995 two engineers, Paul Vixie and Keith Bostic, dug deep enough to find several DEC tapes “under the floor of the computer room [at Bell Labs]” (UNIX Past) which held several original binary files for UNIX. With much help from several individuals, these two engineers were able to reverse engineer the binary tapes they found and 15 years later, put up a repository for this ancient system on GitHub. There it has stayed, waiting for someone to use it like it was meant to be used, on a DEC PDP 11/20, the computer UNIX v1 was initially written for.
the repository of UNIX v1 that can be found on GitHub is at its core the original version of UNIX, but alas, has some makeup of v2. This is where their research ends, and where ours begins.
Here’s Nick Janetakis doing something similar in 2017 using a Docker image of a suitably equipped SIMH:
and there are some related links and pointers in this stackexchange post:
Here’s Warren Toomey in 2010, with First edition Unix: Its creation and restoration
Until recently, the earliest versions of the Unix operating system were believed to have been lost completely. In 2008, however, a restoration team from the Unix Heritage Society completed an effort to resurrect and restore the first edition Unix to a running and usable state from a newly discovered listing of the system’s assembly source code.
… because the PDP-11/20 provided no memory protection against kernel corruption by the running process, it was considered a courtesy for a programmer to yell ‘‘a.out?’’—the name of the Unix assembler’s default output file—before running a new executable for the first time. This gave the other users a chance to save any files they were editing.
(Just for fun, another anecdote from Ritchie’s oddities paper:
at some point several were sitting around working away. Bob Morris asked, almost conversationally, “what are the arguments to ld?” Someone told him. We continued typing for the next minute, as a thought began to percolate, not quite to the top of the brain-- in other words, not quite fast enough. The terminal stopped echoing before anyone could stop and say “Hold on Bob, what is it you’re trying to do?”
Enough time has passed and enough technology invented that some people now can wonder how a multi user OS is even possible without memory protection. Some discussion and links here and here.
Ritchie’s 1979 paper The Evolution of the Unix Time-sharing System is an interesting read.