Abstract: An associative cache and method for replacing data entries in the associative cache by marking input-output (IO) device entries with an IO state. The IO state of a data entry may be indicated by a status or state tag. When valid data entries in a cache must be replaced to make way for new data, entries marked with an IO state are replaced first. This order of replacement improves the cache hit rate by non-IO agents such as data processors by preserving their data entries in the cache. If no valid data entries in the associative cache are marked with an IO state, the method reverts to conventional replacement algorithms such as random or least-recently-used (LRU) to determine which data will be replaced.