A simplified cache with automatic updating for use in a memory system. The cache and the main memory receive data from a common input, and when a memory write operation is performed on data stored at a memory location for which there is a corresponding cache location, the data is written simultaneously to the cache and to the main memory. Since a cache location coresponding to a memory location always contains a copy of the data at the memory location, there is no need for dirty bits or valid bits in the cache resisters and the associated logic in the cache control. The main memory used with the invention may receive data either from a CPU or from I/O devices, and the cache includes apparatus permitting the CPU to perform cache read operations while the main memory is receiving data from an I/O device.
In a memory system having a storage device and a key storage keeping key data controlling an access to the storage device, there is disposed a key address translation structure for obtaining an address of an entry of the key storage based on an address of the storage device to which an access request is issued. As a result, when subdividing the storage device according to the key data setting unit, each subdivided area can be assigned with a variable size and a plurality of sizes are enabled to be specified for the key data setting units at the same time.
A memory device with a dynamic random access memory (DRAM) having an array of a plurality of rows and columns of memory elements; a cache memory formed integrally with the DRAM and includinmg at least one register with a plurality of memory elements and connected in pitch-matched relation to the DRAM array, the number of memory elements in a row of the DRAM being n times the number of memory elements in the at least one register, n being an integer greater than or equal to 2; and a connector for connecting the at least one register to the DRAM, the connector for the at least one register being a bus having a width corresponding to the number of memory elements therein.
A cache memory system operates without requiring valid bits in the external cache tag RAM by employing a system controller as a writeback cache controller for control of the cache data/tag memory and the system main memory. The system controller receives signaling information from a CPU through a host bus to indicate when to pre-load the cache memory or to flush (disable) the cache memory while maintaining memory coherencey by causing the cache controller to write back all modified lines in the cache memory to the main memory.
In a defect relieving technology which replaces defective memory cells of a semiconductor memory device by spare memory cells, use is made of an associative memory. Address information of a defective memory cell is stored as a reference data of the associative memory, and new address information of a spare memory cell is written down as output data of the associative memory. A variety of improvements are made to the associative memory. For instance, a plurality of coincidence detection signal lines of the associative memory are divided into at least two groups, and one group among them is selected by switching means. Reference data of the associative memory comprises three values consisting of binary information of "0" and "1", and don't care value "X". The associative memory further includes a plurality of electrically programable non-volatile semiconductor memory elements.
An incremental garbage collector for use in conjunction with a virtual memory, operates on selected generations of an area upon objects which are contained in a semispace, oldspace or newspace, and during the garbage collection process, all accessible objects are copied from the oldspace to the newspace. The garbage collection process occurs in four phases. In the "flip" phase oldspace and newspace of each generation are exchanged. In the "trace" phase, the pointers which are part of a root set of the generation being collected are traced and all oldspace objects referenced by the pointers are copied to newspace, and the pointers in the root set are updated. All copied objects are then "scavenged" to update any pointers in the cells of the copied objects, and to copy to newspace all oldspace objects referenced by those pointers. Finally a "cleaning oldspace" phase is performed as a low-priority background process to purge the entries for the virtual pages on which "obsolete" pointers reside.
