Temporal codes in on-chip interconnects

Abstract

Dynamic power consumption associated with signal toggles over long distance wires accounts for a significant portion of on-chip interconnect power. Improving dynamic energy efficiency in highly capacitive interconnects can be achieved by reducing the toggle rates associated with data communication. Temporal coding schemes facilitate bounded activity factors by encoding information as placement of signal toggles in time and can thereby improve the energy efficiency of data communication by encoding multiple bits per toggle. We introduce two temporal protocol variants designed for traversal of the crossbars in on-chip networks. These protocols reduce peak power without loss of bandwidth and achieve energy efficient on-chip communication in high capacitance long distance interconnects. Extending these energy savings to a multi-hop mesh topology is achieved by router implementations equipped with bypassing mechanisms that elide per hop reencoding overheads. We demonstrate a four bit per transition temporal protocol with up to 75% communication energy reduction that can be achieved over a baseline serial bit stream protocol.