Memory: cache

Memory hierarchy

As distance from CPU increases, so does size

Fig 7.3

To take advantage of:

temporal locality: keep recently used data closer to CPU

spatial locality: when moving data to a higher level, move a contiguous block

Miss: requested data not found in currrent level

Hit: requested data is found in current level

Hit rate: how often a requested data item is found in a given level of the hierarchy

If hit rate at the top levels of the hierarchy is large, then the average access time

will be close to the fastest access time

Cache: level in hierarchy between CPU and main memory