Energy-efficient encoding techniques for off-chip data buses

Reducing the power consumption of computing devices has gained a lot of attention recently. Many research works have focused on reducing power consumption in the off-chip buses as they consume a significant amount of total power. Since the bus power consumption is proportional to the switching activity, reducing the bus switching is an effective way to reduce bus power. While numerous techniques exist for reducing bus power in address buses, only a handful of techniques have been proposed for data-bus power reduction, where frequent value encoding (FVE) is the best existing scheme to reduce the transition activity on the data buses. In this article, we propose improved frequent value data bus-encoding techniques aimed at reducing more switching activity and, hence, power consumption. We propose three new schemes and five new variations to exploit bit-wise temporal and spatial locality in the data-bus values. Our techniques just use one external control signal and capture bit-wise locality to efficiently encode data values. For all the embedded and SPEC applications we tested, the overall average switching reduction is 53% over unencoded data and 10% more than the conventional FVE scheme.