Patent ID: 6826651
Filing Date: 2004-11-30
Classification: G06F

Abstract:
A system for maintaining consistent cached copies of memory in a multi-node computing system having a main memory comprising:at least one memory directory having memory directory entries mapping the main memory, one or more of the memory directory entries including state information for a corresponding line of main memory; at least one directory cache for storing directory cache lines corresponding to a subset of the memory directory entries, said at least one directory cache disposed within the functionality of a corresponding coherence controller; means for using the state information to allocate memory directory entries to the directory cache; and at least one single-bit sharing history indicator corresponding to each of at least one memory directory, said at least one single-bit sharing history indicator indicating a first value or a second value, wherein the first value indicates that only one node maintains a cached copy of the corresponding line of main memory and the second value indicates that more than one node maintains a cached copy of the corresponding line of main memory.