All of the CMs before the CM-5 were more accelerators than full systems of their own. They sort of look like 90s style GPUs to their host systems. Those host

All of the CMs before the CM-5 were more accelerators than full systems of their own. They sort of look like 90s style GPUs to their host systems. Those host systems were either SunOS, Ultrix, or a Lisp machine. The CM-5 simply ran it's own Unix called CMost, and you'd generally rlogin into it from another Unix machine. In all these cases you could submit batch jobs with NQS (a unix batch system), but you could partition the machine and interactively access it as well, and at the same time as other users or batch jobs.