Correction of incorrect cache accesses

A method of processing data comprising the steps of:

• storing a data item in a storage location within a cache, said storage location being identified by an address, said cache comprising a plurality of storage locations and said cache comprising a cache directory associated with it operable to store an address indicator for each storage location comprising stored data;
• generating a generated hash value from at least some of said bits of said address said generated hash value having fewer bits than said address;
• storing a plurality of hash values relating to said plurality of storage locations within said cache in a buffer;
• in response to a request to access said data item comparing said generated hash value with at least some of said plurality of hash values stored within said buffer and in response to a match indicating a indicated storage location of said data item;
• and
• accessing one of said address indicators stored within said cache directory corresponding to said indicated storage location and in response to said accessed address indicator not indicating said address invalidating said indicated storage location within said cache.

A means for processing data comprising:

• a means for storing data in which a storage location of a data item within said means for storing data is identified by an address, said means for storing data comprising a plurality of storage locations and said data processor comprising a means for storing data directory operable to store an address indicator for each storage location comprising stored data;
• a means for generating a hash value operable to generate a generated hash value from at least some of said bits of said address said generated hash value having fewer bits than said address;
• a data store means operable to store a plurality of hash values relating to said plurality of storage locations within said means for storing data;
• wherein
• in response to a request to access said data item said means for processing data is operable to compare said generated hash value with at least some of said plurality of hash values stored within said data store means and in response to a match to indicate a indicated storage location of said data item;
• and
• to access one of said address indicators stored within said means for storing data directory corresponding to said indicated storage location and in response to said accessed address indicator not indicating said address said data processor is operable to invalidate said indicated storage location within said means for storing data.

A data processor operable to process data, said data processor comprising:

• a cache in which a storage location of a data item within said cache is identified by an address, said cache comprising a plurality of storage locations and said data processor comprising a cache directory operable to store an address indicator for each storage location comprising stored data;
• a hash value generator operable to generate a generated hash value from at least some of said bits of said address said generated hash value having fewer bits than said address;
• a buffer operable to store a plurality of hash values relating to said plurality of storage locations within said cache;
• wherein
• in response to a request to access said data item said data processor is operable to compare said generated hash value with at least some of said plurality of hash values stored within said buffer and in response to none of said at least some of said plurality of hash values matching said generated hash value said processor is operable to:
• initiate a memory access request to access said data item from a memory;
• and
• access at least one further address indicator stored within said cache directory and in response to one of said at least one further address indicator indicating said address said data processor is operable to write said generated hash value to a location within said hash buffer corresponding to said storage location indicated by said at least one further address indicator and to cancel said memory access request.

A method of processing data within a data processor comprising:

• storing a data item in a storage location within a cache, said storage location being identified by an address, said cache comprising a plurality of storage locations and said data processor comprising a cache directory operable to store an address indicator for each storage location comprising stored data;
• generating a generated hash value from at least some of said bits of said address said generated hash value having fewer bits than said address;
• storing a plurality of hash values relating to said plurality of storage locations within said cache in a buffer;
• in response to a request to access said data item:
• comparing said generated hash value with at least some of said plurality of hash values stored within said buffer and in response to none of said at least some of said plurality of hash values matching said generated hash value;
• initiating a memory access request to access said data item from a memory;
• and
• accessing at least one further address indicator stored within said cache directory and in response to one of said at least one further address indicator indicating said address, writing said generated hash value to a location within said hash buffer corresponding to said storage location indicated by said at least one further address indicator and cancelling said memory access request.

A means for processing data comprising:

• a means for storing data in which a storage location of a data item within said means for storing data is identified by an address, said means for storing data comprising a plurality of storage locations and said means for processing data comprising a means for storing data directory operable to store an address indicator for each storage location comprising stored data;
• a means for generating a hash value operable to generate a generated hash value from at least some of said bits of said address said generated hash value having fewer bits than said address;
• a data store means operable to store a plurality of hash values relating to said plurality of storage locations within said means for storing data;
• wherein
• in response to a request to access said data item said means for processing data is operable to compare said generated hash value with at least some of said plurality of hash values stored within said data store means and in response to none of said at least some of said plurality of hash values matching said generated hash value said data processing means is operable to:
• initiate a memory access request to access said data item from a memory means;
• and
• access at least one further address indicator stored within said means for storing data directory and in response to one of said at least one further address indicator indicating said address said means for processing data is operable to write said generated hash value to a location within said hash data store means corresponding to said storage location indicated by said at least one further address indicator and to cancel said memory access request.