New Adaptive Encoding Schemes for Switching Activity Balancing in On-Chip Buses

Abstract

Thermal Spreading has shown to be a successful approach to bus temperature minimization. The idea at the basis of this technique is that of periodically permuting the routing of input bitstreams to the various bus lines, with the objective of temporally and spatially distributing the number of transitions over the entire bit-width, thus avoiding high switching activities to occur always on a few lines, which obviously causes an unnatural increase in temperature. In this paper, we propose new encoding schemes which improve the capabilities of the Thermal Spreading approach of balancing the switching activities over the bus wires. The solutions we introduce are adaptive and dynamic in nature, as they select what bitstream goes to what bus line based on the actual bus traffic, thanks to some on-line monitoring capabilities which is offered by some ad-hoc hardware unit which runs in parallel at the transmitting and receiving ends of the bus. The experimental results show that, on average, the proposed encoding schemes improve the transition balancing capabilities of the Thermal Spreading technique by a significant amount.