Computer Processor Employing Cache Memory With Per-Byte Valid Bits

Abstract

A computer processing system with a hierarchical memory system that associates a number of valid bits for each cache line of the hierarchical memory system. The valid bits are provided for each cache line stored in a respective cache and make explicit which bytes are semantically defined and which are not for the associated given cache line. Memory requests to the cache(s) of the hierarchical memory system can include an address specifying a requested cache line as well as a mask that includes a number of bits each corresponding to a different byte of the requested cache line. The values of the bits of the byte mask indicate which bytes of the requested cache line are to be returned from the hierarchical memory system. The memory request is processed by the top level cache of the hierarchical memory system, looking for one or more valid bytes of the requested cache line corresponding to the target address of the memory request. The valid bytes of the cache line corresponding to the byte mask as stored in cache can be identified by reading out the valid bit(s) and data byte(s) stored by the cache for putative matching cache lines for those data bytes that are specified by the byte mask of the memory request, while ignoring the valid bit(s) and data byte(s) stored by the cache for putative matching cache lines for those data bytes that are not specified by the byte mask of the memory request. Extensions to shared multiprocessor systems is also described and claimed.

Dependencies are inferred from the claim text.