RSTS-11 (not RSTS/E) ran on the 11/20. It offered multiuser timesharing in BASIC. I think that in addition to the base 11/20 hardware, you needed a clock. You needed to max out the memory (28 Kwords).
V4 was the last RSTS-11 release before it became RSTS/E.
System manager's manual for RSTS-11.
I have not checked to see if there are software kits available....
Manchester MUSS ran on a PDP11/10, but I can't offer a working PDP11 image for it at the moment as it is lost in passage of time....
It would have been able to do its own memory management and swap, multitasking etc.
Note: this is mostly guesswork
I don't know this assembler but the f suffix seems to denote a label. Example
Those instructions write the parameters in the parameter zone of the system call.
note that there's a 0 label just after the sys instruction. It holds the parameters (copies of those which ...
So bare metal, no OS?
On both systems, console terminal I/O is considerably easier than any other terminal interface.
On many VAXen, there's a couple of processor registers that are status and data registers for console I/O. Much easier than dealing with DZ-11 or similar.
Here's the important part of a VAX 'putchar' routine from a standalone libc I wrote in ...
Not an answer, as Jean-François Fabre has already deducted all workings, but some hints about the syntax/workings of AS to understand the source.
This source is meant to be assembled using the Unix assember AS. AS is an extreme primitive assembler designed only to handle machine specific parts of Unix. It carries only the most essential functions and those ...
There was LSX - a small, single-user UNIX for non-MMU PDP-11's based on UNIX V6. It also ran on the LSI 11/03. It was "interesting" to hear the RX01 floppies clunk and chatter when running piped commands!
LSX Unix Restoration Page
... LSX needed at least 40 kbytes. That's 20 kilowords: 8 kilowords
... for the system and ...
My primary experience on a PDP-11 class machine was using Forth. We were using it for high-end (at the time) image processing and display algorithms. The advantage is that it is very compact and quick. If you need quicker, you can write "words" (that's Forth for subroutines) incorporating assembly. From a modern perspective, Forth might not ...