Using adaptive routing to compensate for performance heterogeneity

Scalable and power efficient multi-core architectures must be performance heterogeneous to accommodate semi-conductor parametric variations and non-uniform access to shared resources. Due to its rate matching, a NoC on a Voltage-Frequency Island architecture can connect cores without forcing each one to give up its own operating point for the chip-wide common worst case. With run-time adaptive routing and task-to-core mapping, a NoC can run at the average not the worst case network saturation bandwidth. These run-time processes compensate for variations because they match application resource requirements with heterogeneous cores and routers. We focus on adaptive routing that simultaneously combats communication load imbalance from on-die variations and application topology. We show that even with static, fixed task-to-core mapping on multi-core architectures affected by stochastic variations, our MATC router increases the expected saturation bandwidth by 7-25% vs Dimension Order router. With systematic variations, the improvements are 5-50%. These gains compensate for saturation bandwidth degradation due to manufacturing variations and help to reduce design guard-bands.