_Ahem_. It ran under VM/370. Most (all?) models of the IBM 370 had virtual memory, as had the (not widely-available) 360/67. OS/360 is one of several operating systems for the IBM 360 and successors. I grabbed the Princeton v7-to-370 port sources, and I have a VM/370 r6 machine set up on Hercules, but I have not yet made the attempt to combine the two. Many years after that, also at Princeton, I sysadminned PenguinVM, which as far as I know was the first publicly-available Linux/390 machine. Adam