Multiprocessor system with each processor executing the same instruction

Abstract

A computer system employs multiple CPUs, all executing the same instruction stream, with multiple, identical memory modules storing duplicates of the same data and accessable by all the CPUs, providing global memory. The multiple CPUs are loosely synchronized, as by detecting events such as memory references and stalling any CPU ahead of others until all execute the function simultaneously. Each CPU has its own fast cache and also a local memory not accessable by the other CPUs. A hierarchical virtual memory management arrangement for this system employs demand paging to keep the most-used data in the local memory, page-swapping with the global memory. Page swapping with disk memory is through the global memory; the global memory is used as a disk buffer and also to hold pages likely to be needed for loading to local memory. The operating system kernal is kept in local memory. This arrangement is particularly useful in fault-tolerant computer systems.