International Business Machines Corporation

Nobuyuki Harada

Takeo Nakada

Nobuyuki Ohba

A memory apparatus having a cache memory including cache segments, and memorizing validity data indicative of whether or not each of the sectors contained in each cache segment is a valid sector inclusive of valid data; and a cache controlling component for controlling access to the cache memory. The cache controlling component includes a detecting component for detecting, when writing a cache segment back to the main memory, areas having consecutive invalid sectors by accessing validity data corresponding to the cache segment, and a write-back controlling component issuing a read command to the main memory, the read command being for reading data into each area detected, making the area a valid sector, and writing the data in the cache segment back to the main memory.

Technique and apparatus for identifying cache segments for caching data to be written to main memory

To ensure efficient access to a memory whose writing process is slow. There is provided a storage device for caching data read from a main memory and data to be written in the main memory, comprises a cache memory having a plurality of cache segments, one or more cache segments holding data matching with data in the main memory being set in a protected state to protect the cache segments from a rewrite state, an upper limit of a number of the one or more cache segments being a predetermined reference number; and a cache controller that, in accordance with a write cache miss, allocates a cache segment selected from those cache segments which are not in the protected state to cache write data and writes the write data in the selected cache segment.

System for caching data from a main memory with a plurality of cache states

To improve the efficiency of access to a system memory associated with changes (writes) to cache data, a cache line having the same memory size as write data is selected and the write data is written into the selected cache line, thereby reducing the number of accesses to the system memory to cache data from the system memory associated with partial replacement of cache lines. Further, valid data at an address contiguous with the address of the write data is combined with the write data, and written into a cache line having the same size as the combined data, thereby reducing the number of accesses to the system memory to flush data from the cache associated with writes to the cache.

Cache memory system and control method of the cache memory system

A memory system including a bus, a memory, a memory controller, a first devicehaving a cache, and a second device, all connected to the bus, wherein the memory controller includes a bufferfor temporarily storing cache data and write data that the second device writes in the memory. The buffer of the memory controller temporarily stores cached data and the write data to be written on write access to the memory by the second device, which enables maintenance of data coherency while avoiding a write access retry by the second device.

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Machida, Japan

Nobuyuki Harada