Directory cache for a plurality of caches stores information about copies of memory lines stored in the caches.

摘要

A directory cache (120b) comprises a plurality of directory entries (500, 502, 504, 506, 508, 510) configured to store information regarding copies of memory lines stored in a plurality of caches. The entries are divided into sets of N entries (500, 502, 504), with each set of N entries being addressable via an index. A cache controller (512) which retrieves a set of N entries (500, 502, 504) associated with an index corresponding to a memory line. If a tag portion of one of the retrieved entries (500) corresponds to the memory line, the cache controller determines whether the one of the retrieved entries contains an indication that information regarding the memory line is stored in at least a second one of the retrieved entries (502). The information stored in the second retrieved entry may indicate which other caches store the memory line, which may be a share vector. The format of the bits in the retrieved entry differs depending on whether a memory line is stored in M or fewer caches. Information about the memory line is stored in a single directory entry. When a copy of the line appears in more than M caches two entries are made, each with data indicating the other entry.