Multi-microprocessors: An overview and working example

Rapid and continuing advances in large-scale integrated (LSI) semiconductor technology have lead to considerable speculation on ways to exploit microprocessors for building computer systems. Microprocessors are being applied very successfully where small amounts of computing power ate needed, such as in calculators, instruments, controllers, intelligent terminals, and more recently in consumer goods and games; but it remains an open problem to design a commerdally viable multiple-microprocessor structure. A variety of organizations have been proposed for such systems, and this article begins with an overview of this spectrum. Few multiple-microprocessor systems, however, have been built or otherwise subjected to a critical analysis. To address the unresolved problems facing such systems, Carnegie-Mellon University has undertaken the design, implementation, and evaluation of an experimental multi-microprocessor computer system called Cm^*. A 10-processor, ½ Mbyte primary memory prototype configuration of Cm^*has been completed and became available for experimentation in the Spring of 1977. The kernel of an operating system and five application programs with widely varying characteristics have been written for Cm^*, and form the basis for the measurements and discussion given here. Several of the application programs have been able to utilize all the processors in the prototype system effectively. In other words, doubling the number of available processors effectively doubled the execution speed of these programs.