Switching Activity Minimization by Efficient Instruction Set Architecture Design

Power consumption can be greatly minimized by reducing the bus signal transition activity (also called switching activity) in the control and data path circuit. Switching activity occurs due to the switching between two instructions (of the embedded software) on successive clock cycles. Our belief is that the binary encoding of instructions (machine code) plays a significant role in determining the amount of switching in a circuit. Thus, our aim is to realise a machine encoding of instructions of an ASIP such that for a given data path, it will minimize the average switching activity in the control path circuit of the ASIP and hence the total switching activity in the ASIP. Given the application-domain of the ASIP, we have used information theoretic techniques to arrive at an encoding of the op-code that minimizes redundancy and also the switching activity. We have compared our encoding of instruction op-codes with those obtained by other encoding techniques using a switching activity estimator designed by us.