The SPEED cache coherence protocol for an optical multi-access interconnect architecture

The paper presents a low overhead, high performance cache coherence protocol designed to exploit high bandwidth point to point and broadcast features of optics. SPEED integrates the virtues of snoopy based schemes and directory based schemes into one efficient protocol. Directory assist is used exclusively for read traffic to eliminate unnecessary broadcasts while snoopy assist is used exclusively for write and synchronization traffic to reduce directory overhead and synchronization complexities. The proposed protocol has the potential to increase performance as a result of its global independence between read and write operations, concurrency in channel access, reduced contention, and efficient broadcast of coherence and synchronization events.