A probabilistic model for the evaluation of microprogram performance

Abstract

This paper reports the development of a probabilistic model of microprogram behavior and the application of this model to the measurement of some fundamental parameters of microprogram performance. The major parameters considered are: (a) the mean microinstruction reference time, (b) the degree of parallelism in microprograms, and (c) the effect of branch microinstructions on performance degradation. The execution of each independent machine instruction invokes a specific sequence of microinstructions from the corresponding microprogram. It is shown that for a specific class of microprograms, the above parameters may be quantitatively determined, given the probabilities of machine instructions, and the conditional probabilities of the microinstruction sequence corresponding to a particular machine instruction. Examples are given for some representative machine instructions.