Patent ID: 6314491
Filing Date: 2001-11-06
Classification: G06F

Abstract:
A memory-cache system for use in a multiprocessor environment in which memory accesses are generated by first and second processors, the system comprising:a shared lower level storage system, which comprises a lower level cache and a main storage, the lower level cache maintaining copies of data in main storage,a first cache configured for connection to said lower level storage system and said first processor, receiving from said first processor memory access commands identifying data to be stored in said lower level storage system or data to be loaded from said lower level storage system, said first cache loading data from and storing data to said lower level storage system in response to said memory access commands,a second cache configured for connection to said lower level storage system and said second processor, receiving from said second processor memory access commands identifying data to be stored in said lower level storage system or data to be loaded from said lower level storage system, said second cache loading data from and storing data to said lower level storage system in response to said memory access commands,a cache storage control circuit, the storage control circuit managing loading of data from said lower level storage system to said caches and storing of data to said lower level storage system from said caches,wherein, said lower level storage system maintains an indication of whether the first or second caches are storing copies of data, and whether those copies have been modified, andupon receipt from said first cache of a request for data that has been modified by said second processor and is stored in modified form in said second cache, said storage control circuit causes said second cache to transfer said data to said first cache without returning said data to said shared lower level storage system,whereby the effect of repeated writes to the same data by the first and second processors is ameliorated.