cache tag

The high bits of an address, stored beside each cached line so the cache can tell which of the many possible lines is the one sitting there.

The tag is the address field above the index and offset; a lookup compares the stored tag of each candidate line with the address's tag, and a valid line whose tag matches is a hit.

Examples

In a 32 KiB direct-mapped cache with 64-byte lines, every address bit above the low 15 is the tag.