On the Use of Simple Electrical Circuit Techniques for Performance Modeling and Optimization in VLSI Systems

Leading-edge VLSI systems, essentially multiprocessor systems-on-chip, have a wide range of components integrated together and operating in unison. They can be analyzed as flow networks in which the system performance depends on the bandwidth, transmission time, and queueing delay characteristics of the individual components, their connectivity and interactions, as well as the traffic patterns they encounter. The flow in various parts of the system must ideally be distributed so as to extract the maximum throughput possible with minimum end-to-end delays. Such an ideal distribution for flow networks has previously been obtained using simple electrical circuits. We demonstrate a similar methodology for typical VLSI systems and provide the necessary extensions of the theory. We empirically validate the methodology using a cycle-accurate simulation model as the reference. We find this methodology to supply better distributions in the average case and comparable distributions in the worst case as compared to standard search procedures such as random sampling and simulated annealing. The real strength is that it provides a speedup of several orders of magnitude, i.e., 3-5 orders in our experiments. Thus it is an elegant means for analyzing and optimizing the flow in VLSI systems, which can easily be incorporated into design procedures, compilers and on-chip modules for real-time allocations.