Comparative Survey of Different Design Methodologies for Control Part of Microprocessors

We present several methodologies used in the design of control parts of microprocessors and we discuss their classification with respect to the qualities of the design. All these different methodologies were brought out by decoding existing integrated circuits. Afterwards each one of these methodologies was used to redesign a new control part of the MC 6800 microprocessor, its operation part remaining unchanged. By so doing, we obtained a set of normalized solutions so that the real efficiency of each method could be estimated in terms of the cost of hardware and design time. The performance expressed by the cycle time of each control part was also calculated leading to the complete, valid classification of different design styles. At last the evolution of the design efficiency versus the circuit complexity was studied.