A Study in Microprogrammed Processors: A Medium Sized Microprogrammed Processor

Abstract

A frame of reference is established for evaluating the various philosophies or approaches to the microprogramming of control logic. Three new measures for analyzing microprogramming philosophies are introduced: "monophase" versus "polyphase," "parallel" versus "serial," and "encode" versus "little encode." The terms monophase, polyphase refer to how long the microinstruction is valid. Parallel, serial refer to the method used to determine the next instruction to be executed. Encode, little encode refor to the degree of encoding in the microinstruction word. The relative merits of the extremes of these new measures are discussed. Then an example of the use of microprogramming for control logic is explored; specifically Univac's C/SP Processor is microprogrammed. It is then shown that this processor would have a cost and performance comparable with the actual C/SP version now being tested which uses conventional control logic. Moreover, it would have the flexibility and simplicity inherent in microprogramming.