Within-Die Variation-Aware Dynamic-Voltage-Frequency-Scaling With Optimal Core Allocation and Thread Hopping for the 80-Core TeraFLOPS Processor

In this paper, we present measured within-die core-to-core Fmax and leakage variation data for an 80-core processor in 65 nm CMOS and 1) populate a parameterized energy/performance model to determine the most energy-efficient operating point for a workload; 2) examine impacts of per-core clock and power gating on optimal dynamic voltage-frequency-core scaling (DVFCS) operating points; and 3) compare improvements in energy efficiency achievable by variation-aware DVFCS and core mapping on Single-Voltage/Multiple-Frequency (SVMF), Multiple-Voltage/Single-Frequency (MVSF) and Multiple-Voltage/Multiple-Frequency (MVMF) designs. Variation-aware DVFS with optimal core mapping is shown to improve energy efficiency 6%-35% across a range of compute/communication activity workloads. A new dynamic thread hopping scheme boosts performance by 5%-10% or energy efficiency by 20%-60%.