Fractal Coherence: Scalably Verifiable Cache Coherence

We propose an architectural design methodology for designing formally verifiable cache coherence protocols, called Fractal Coherence. Properly designed to be fractal in behavior, the proposed family of cache coherence protocols can be formally verified correct for systems with an arbitrary number of cores, using existing, automated formal tools. We show, by designing and implementing a specific Fractal Coherence protocol, called Tree Fractal, that Fractal Coherence protocols can attain comparable performance to traditional snooping and directory protocols.