The evolution of virtual machine architecture

In the early 1960's two major evolutionary steps were taken with regard to computing systems architecture. These were the emergence of I/O processors and the use of multiprogramming to improve resource utilization and overall performance. As a consequence of the first step computing systems became multiprocessor configurations where nonidentical processors could have access to the common main memory of the system. The second step resulted in several computational processes sharing a single processor on a time-multiplexed basis while vying for a common pool of resources.