Performance and Power Benefits of Sharing Execution Units between a High Performance Core and a Low Power Core

Several studies and real world designs have advocated the sharing of large execution units between pairs of cores in Symmetric Multicore Processors (SMP) for area and power savings. Such sharing was shown to have negligible impact on performance. Recently, a number of Asymmetric Multicore Processor (AMP) designs have become available. The objective of this paper is to investigate whether sharing of resources across AMPs offers similar benefits. Our study shows that while the area and the power savings remain similar, the performance of the smaller core in the AMP can improve significantly making sharing even more attractive for AMPs. Simulation results indicate that for certain workloads, the performance of the small core may improve by as much as 54% by sharing certain large execution resources of the big core, while affecting the performance of the big core by only ~4%, resulting in an overall gain in system performance of 20%. The corresponding improvement in aggregate performance/Watt is 12% while the area savings is about 7%.