Federation

Abstract

Manycore architectures designed for parallel workloads are likely to use simple, highly multithreaded, in-order cores. This maximizes throughput, but only with enough threads to keep hardware utilized. For applications or phases with more limited parallelism, we describe creating an out-of-order processor on-the-fly, by federating two neighboring in-order cores. We reuse the large register file in the multithreaded cores to implement some out-of-order structures and reengineer other large, associative structures into simpler lookup tables. The resulting federated core provides twice the single-thread performance of the underlying in-order core, allowing the architecture to efficiently support a wider range of parallelism.