The PDP-11 virtual machine architecture: A case study

Abstract

At UCLA, a virtual machine system prototype has been constructed for the Digital Equipment Corporation PDP-11/45. In order to successfully implement that system, a number of hardware changes have been necessary. Some overcome basic inadequacies in the original hardware for this purpose, and others enhance the performance of the virtual machine software. Steps in the development of the modified hardware architecture, as well as relevant aspects of the software structure, are discussed. In addition, a case study of interactions between hardware and software developments is presented, together with conclusions motivated by that experience.