A SPEED Cache Coherence Protocol for an Optical Multi-Access Interconnect Architecture

This 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. 1 Introduction Caches play a critical role in reducing interconnect traffic and latency in shared memory multiprocessors (SMMPs) by maintaining local copies of shared data. An important factor that determines the performance of cached SMMP..