System and method to enter and exit a cache coherent interconnect

Abstract

A cache coherent interconnect connected to one or more agents, using Network Interface Units (NIUs), and also having one or more internal modules, such as a directory, is provided with one or more message builders and message receivers. These message builders and message receivers are provided as additional hardware IP blocks incorporated into the various NIUs and modules. When an agent signals an intention to enter/exit the cache coherent interconnect, a message communicating this information is generated using message builders, and transmitted using the interconnect wiring as a 'virtual wire' to one or more message receivers associated with directories that need to be aware of the entry/exit transition of the agent. The directories are provided with tracking engines to manage the entry/exit information and status of the agent. Interconnects may include a broadcast engine to provide distribution to, and aggregate acknowledgements from, a single source to multiple destinations.