Abstract: A snoop filter maintains data coherency information for multiple caches in a multi-processor system. When a new request for a memory line arrives, an entry of the snoop filter is selected for replacement if there is no available slot in the snoop filter to accommodate the new request. The selected entry is among the entries predicted to be short-lived based on a coherency state. An invalidation message is sent to the one of the caches with which the selected entry is associated.

Abstract: A system and method for maintaining data coherency in a multiprocessor environment. The system includes a snoop filter that maintains a representation of the organization and context of each last level cache on the system. The representative is updated with each request which each include a hint to the location where requested data will be stored in the last level cache.

Abstract: A method for reducing memory latency in a multi-node architecture. In one embodiment, a speculative read request is issued to a home node before results of a cache coherence protocol are determined. The home node initiates a read to memory to complete the speculative read request. Results of a cache coherence protocol may be determined by a coherence agent to resolve cache coherency after the speculative read request is issued.

Abstract: A method and apparatus for a mechanism for handling explicit writeback in a cache coherent multi-node architecture is described. In one embodiment, the invention is a method. The method includes receiving a read request relating to a first line of data in a coherent memory system. The method further includes receiving a write request relating to the first line of data at about the same time as the read request is received. The method further includes detecting that the read request and the write request both relate to the first line. The method also includes determining which request of the read and write request should proceed first. Additionally, the method includes completing the request of the read and write request which should proceed first.

Abstract: In some embodiments, an apparatus includes a processor, an expander memory bridge location, a memory coupled to the expander memory bridge location, and a bus controller including intercept logic to intercept and block communication from the processor to the expander memory bridge location and to emulate an expander memory bridge. In some embodiments, a method includes intercepting and blocking a status request to a device, regardless of whether the device is installed, and responding to the status request.

Abstract: A method for processing an atomic transaction in a multi-bus system that includes a local bus and a remote bus. According to the method, a first transaction in an atomic sequence is received from the local bus. The first transaction is terminated on the local bus. The first transaction is performed on the remote bus. A response to the first transaction is received and the response is placed on the local bus.