A cache-and-overflow memory handles both cache and overflow data in a single hardware structure so as to increase speed and reduce supporting hardware structure needed to implement an effective memory system. A single hash value can be used to access either a cache data value or an overflow data value stored in the combined cache-and-overflow memory. If there are a small number of overflow entries, the combined cache-and-overflow memory provides more availability for cache entries. However, overflow entries are provided priority over cache entries. As a result, the combined cache-and-overflow memory dynamically reallocates its space to efficiently store as much as cache as possible until space is needed for overflow data. At that time, the cache data is evicted in a priority order to make space for the overflow data.