A survey on bit dimension optimization strategies of microprograms

Microprogram optimization is one way to increase efficiency, and optimization can be crucial in some applications. Optimization refers to a reduction of execution time of microprograms, or of the control store size, B×W, where W represents the word dimension of the control store which is the number of words of control store required for certain application, and B represents the bit dimension which is the number of bits per word of control store. The various optimization strategies can be broadly classified under four categories: bit dimension reduction, word dimension reduction, state reduction, and heuristic reduction. A survey of the various bit dimension optimization techniques has been presented by Agerwala in his 1976 paper, where the techniques are critically analyzed and compared, and the results of analysis are discussed. The paper further augments the work of Agerwala, taking into account the optimization methods developed later and hence not discussed by him. Also, the present study considers the optimization problem in the case of polyphase microinstructions in addition to that for monophase microinstructions. The prospective, current status, and future trends in this direction are also briefly outlined