Information processing apparatus in which a cache memory can be operated in both store-in and store-through modes

A cache memory control method for use in an information processing apparatus composed of a main storage, for storing a plurality of blocks of data, and a plurality of processor units, said processor units each including a processor having a control status register for storing information about the processor's control status, a private cache memory associated with said processor and said main storage, and a cache memory controller associated with said processor and said private cache memory, said method comprising the steps of:

• a) providing a read-request for reading a block of data from one of said processors to the cache memory controller associated therewith, said read-request including information indicating an address for designating a storage location of the main storage where the data to be read is stored;
• b) in the cache memory controller which has received said read-request from the associated processor, loading the block of data from a storage location of said main storage, designated by the address information included in said read-request, into a storage location of the associated private cache memory if said block of data is not already present in the private cache memory, discriminating, based on information in said control status register, whether the requested data is to be controlled using a store-in system or a store-through system, and storing a flag indicating the discriminated system in relation to the storage location of the associated private cache memory where said block of data was loaded;
• and
• c) updating a block of data stored in said main storage with a corresponding block of data stored in the private cache memory associated with said cache memory controller using a store-through system if the stored flag in said cache memory controller related to the storage location of the private cache memory where said corresponding block of data is stored indicates that said block of data is to be controlled using a store-through system, and updating said block of data stored in said main storage using a store-in system if the stored flag in said cache memory controller related to the storage location of the private cache memory where said block of data is stored indicates that the block of data is to be controlled using a store-in system.

An information processing apparatus comprising:

• (a) a main storage for storing a plurality of data;
• and
• (b) a plurality of processor units each including a processor, a private cache memory coupled to said processor, and a cache memory controller which controls said cache memory and is coupled to said cache memory and said processor;
• 1) each processor comprising:
• a) means for generating a read-request for reading data from said main storage, said read-request including information indicating whether the data requested by the read request is to be controlled using a store-through system or a store-in system;
• b) a control status register for storing information about the processor's control status;
• and
• c) means for outputting the generated read-request to the cache memory controller associated with that processor;
• and
• 2) each cache memory controller comprising:
• a) means for storing a plurality of flags, each flag corresponding to a respective one of the data stored in the private cache memory associated with the cache memory controller and each indicating whether the corresponding data is to be controlled using the store-through system or the store-in system;
• b) means for loading data requested by a received read-request from said main storage into the cache memory associated with the cache memory controller if the requested data is not present already in the associated cache memory;
• c) means for setting the flag corresponding to the data loaded in the associated cache memory according to said information, included in the received read-request which caused the loading, in said control status register;
• and
• d) means for controlling an operation of updating a storage location of said main storage with the data stored in a corresponding storage location of the cache memory associated with the cache memory controller using the store-through system if the flag corresponding to the data stored in said corresponding storage location of the cache memory indicates that the data is to be controlled using the store-through system, and controlling said updating operation using said store-in system if said stored flag corresponding to the data stored in said corresponding storage location of the cache memory indicates that the data is to be controlled using the stored-in system.

An information processing apparatus for performing a plurality of processes, said information processing apparatus comprising:

• (a) a main storage for storing a plurality of data divided into a plurality of blocks of data;
• and
• (b) a plurality of processor units each including a processor for executing a process or processes, a private cache memory coupled to said processor and a cache memory controller which controls said cache memory and is coupled to said cache memory and said processor;
• 1) each processor comprising:
• a) means for generating a read-request for reading data from said main storage, said read-request including information indicating whether the data requested by the read request is to be controlled using a store-through system or a store-in system;
• b) a control status register for storing information about the processor's control status;
• and
• c) means for outputting the generated read-request to the cache memory controller associated with that processor;
• and
• 2) each cache memory controller comprising:
• a) means for loading a block of data including the data requested by a received read-request from said main storage into the cache memory associated with the cache memory controller if the requested block of data is not present already in the associated cache memory;
• b) means for storing a plurality of flags each of which corresponds to a respective one of the blocks of data stored in the cache memory associated with the cache memory controller, each of said flags indicating whether the corresponding block of data is to be controlled using said store-through system or store-in system;
• c) means for setting the flag corresponding to the block of data loaded in the associated cache memory according to said information included in the received read-request which caused the loading;
• and
• d) means for controlling an operation of updating a storage location of said main storage with the block of data stored in the corresponding storage location of the cache memory associated with the cache memory controller using the store-through system if the flag corresponding to said corresponding block of data stored in said corresponding storage location of the cache memory indicates that the block of data is to be controlled using the store-in system.