https://www.msu.edu/~mrr/mycomp/terak/termubel.htm Lycklama's MINI-UNIX on an PDP-11/03, early 1980s for my first experience. MINI-UNIX was a cutdown UNIX V6 kernel that operated on a PDP-11 without MMU support, by swapping each process in and out of what little memory remained (12KW for the kernel and 16KW for user space). What made it somewhat usable for us was the very fast optically-positioned Pertec fixed/cartridge disk system (emulated an RK05) we had on the system at the time. It was essentially a single user environment, but the C compiler worked. I think we briefly tried two terminals (ADM3a) just to see if it would work. That experience lead us to later get an LSI-11/23 CPU board and additional memory and start running UNIX V7, and for a brief time we had 12 terminals connected with students able to do a mix of Pascal and simple FORTRAN programs (no one wanted to use C at that stage).