Within-Die Variation-Aware Scheduling in Superscalar Processors for Improved Throughput

Abstract—Within-die parameter variations can cause wide delay distribution among similar functional units in superscalar processors. Conventionally, the frequency of operation is reduced to accommodate the slowest unit, which in turn degrades throughput. We present a low-overhead design technique that sets the operating frequency in a superscalar processor based on the faster units and allows more cycles for the slower units. We propose an associated priority scheduling strategy to schedule instructions in the functional units to maximize throughput. Simulation results on a set of benchmarks show that, by assigning a higher scheduling priority to faster units, we can achieve 18 percent improvement in performance on average with negligible design overhead. Index Terms—Superscalar processors, scheduling, heterogeneous functional unit, process variation, speed binning. Ç