The Sun Fireplane System Interconnect

System interconnect is a key determiner of the cost, performance, and reliability of large cache-coherent, shared-memory multiprocessors. Interconnect implementations have to accommodate ever greater numbers of ever faster processors. This paper describes the Sun™ Fireplane two-level cache-coherency protocol, and its use in the medium and large-sized UltraSPARC-III-based Sun Fire™ servers.