Analyzing impact of multiple ABB and AVS domains on throughput of power and thermal-constrained multi-core processors

Recently, semiconductor industries have integrated more cores in a single die, which substantially improves the throughput of the processors running highly-parallel applications. However, many existing applications do not have high enough parallelism to exploit multiple cores in a die, slowing the transition to many-core processors with smaller and more cores that benefit future applications with high parallelism. In this paper, we analyze the impact of multiple adaptive voltage scaling (AVS) and adaptive body biasing (ABB) domains on the throughput of power and thermal-constrained multi-core processors when they are combined with per-core power-gating (PCPG). Both AVS and ABB can be effectively used to either increase frequency (thus throughput) or decrease power consumption of the processors. Meanwhile, PCPG can provide extra power and thermal headroom when application's parallelism is limited. First, we analyze the throughput impact of applying AVS, ABB, and PCPG for power and thermal constrained multi-core processors. Second, we investigate the impact of multiple AVS and ABB domains on the throughput, and recommend the most cost-effective number of domains for AVS and ABB in 16 and 8-core processors. Our analysis using the 32nm predictive technology model considering within-die variations suggests that the most cost-effective number of domains for AVS and/or ABB should be one for each when they are combined with PCPG in both 16 and 8-core processors. Since within-die core-to-core variations provide many choices in terms of core frequency and power consumption for limited-parallelism applications, one AVS or ABB domain can leads to the throughput improvement by 1.77∼2.49x; more than one AVS and/or ABB domains only improve the throughput marginally.