Demand-Only Broadcast: Reducing Register File and Bypass Power in Clustered Execution Cores

This paper introduces a technique called Demand-Only Broadcast that reduces the power consumption of the register file and result bypass network in a clustered execution core. With this technique, an instruction’s result is only broadcast within remote clusters if it is needed by dependants in those clusters. Demand-Only Broadcast was evaluated using a performance–power simulator of a high-performance clustered processor which already employs techniques for reducing register file and instruction window power. By eliminating 59% of the register file writes and intra-cluster broadcasts, the total processor power consumption (including the hardware needed by this mechanism) is reduced by 10%, while having less than a 1% impact on IPC. DemandOnly Broadcast also results in a 10% higher IPC and 4% lower power consumption than a clustered processor with a partitioned register file.