Preventive Cast Out Operations in Cache Hierarchies
Original Publication Date: 1981-May-01
Included in the Prior Art Database: 2005-Feb-11
In storage hierarchies with a high-speed buffer (cache 1) interposed between the main storage (basic storage module (BSM)) and processor, modification of the stored data is often performed according to the "store in cache" principle, in which only the cache block is changed but not its replica in main storage. The change is noted by a change bit in column 3 of cache directory 2. The main storage block is updated only when its cache block is to be overwritten by a new block following a cache miss; in such a case, the modified cache block has to be written back into main storage before the respective cache area can be released. Thus, access to the new cache block which caused a cache miss is delayed by this "cast-out" operation into main storage.