VPS/VM (Virtual Processing System/Virtual Machine) was an operating system that ran on IBM System/370 – IBM 3090 computers at Boston University in general use from 1977 to around 1990, and in limited use until at least 1993. During the 1980s, VPS/VM was the main operating system of Boston University and often ran up to 250 users at a time when rival VM/CMS computing systems could only run 120 or so users.
Each user ran in a Virtual Machine under VM, an IBM hypervisor operating system. VM provided the virtual IBM 370 machine which the VPS operating system ran under. The VM code was modified to allow all the VPS virtual machines to share pages of storage with read and write access. VPS utilized a shared nucleus, as well as pages used to facilitate passing data from one VPS virtual machine to another. This organization is very similar to that of MVS; substituting Address Spaces for Virtual Machines.