Cooling codes: Thermal-management coding for high-performance interconnects

High temperatures have dramatic negative effects on interconnect performance. Numerous techniques have been proposed to reduce the power dissipation of on-chip buses but they fall short of fully addressing the thermal challenges posed by high-performance interconnects. We introduce new efficient coding schemes that directly control the peak temperature of a bus by effectively cooling its hottest wires. This is achieved by avoiding state transitions on the hottest wires for as long as necessary until their temperature drops off. At the same time, we reduce the average power consumption by ensuring that the total number of state transitions on all the wires is bounded. Our solutions call for redundancy: we use n > k wires to encode a given k-bit bus. Therefore, it is important to determine the minimum possible number of wires n needed to encode k bits while satisfying the desired properties. We provide full analysis in each case, and show that the number of additional wires required to cool the t hottest wires is negligible when k is large. Moreover, the resulting encoders and decoders are fully practical. They do not require significant computational overhead and can be implemented without sacrificing a large circuit area.