A cache-status maintaining unit stores address information of data stored in each entry of a cache memory, and maintains a status of each entry as any one of \u201cstrongly modified\u201d, \u201cweakly modified\u201d, \u201cshared\u201d, and \u201cInvalid\u201d. This is accomplished in part by a pair of switches included in the current mirror, which are controlled by enable signals. The third region of the structure is disposed between the first and second regions.