I'm curious about what various people think defines a mainframe. IBM people clearly have something in mind, and DEC people something else. Maybe DG had yet another definition.
A mainframe is a high-RAS (reliability, availability, serviceability), high-performance, high-cost, modular multiprocessor machine with specialized coprocessors; running a hypervisor-style operating system that is largely concerned with allocating resources and managing security partitions. Interconnections among modules happen at system bus latencies and bandwidths.
zabzonk is technically correct, which is the best kind of correct. I was using 'mainframe' colloquially and lazily. DG's mini line was used for the same kinds of things as mainframes, but they were formally minis at the time.
