The Modeling and Synthesis of Bus Systems

A bus oriented interconnection of registers and data operators is the dominant mode of design for the data paths of digital systems. A study of ten processor implementations, ranging in size from microprocessors to large mainframes, spanning almost 20 years in the practice of digital design, indicated a strong similarity. From this study bus style primitives and generic bus models were developed. The generic bus models were simplified to match each of the ten processors composing the study. An algorithm for generating a bus style design is presented. The algorithm is used to generate the data paths of the PDP-11/40 resulting in lower cost and shorter delays than the original implementation. Finally, the paper concludes with a discussion of the bus synthesis algorithm´s implementation and its role in the CMU functional-to-hardware Design Automation System.