Memory: levels

Data is transferred only between adjacent levels:

When miss occurs at one level of hierarchy, data is transferred from next lower level

Minimum unit of data transferred: block

Performance depends on speed of hits and misses

Hit time: time to access upper level,

including determining hit or miss

Miss penalty: time to access lower level to get data

Issues

How much data to transfer between levels

Policy to replace data in upper levels

Policy to update data in each level

Analogy

Need 10 books for a term paper

Fig. 7.2

Bring all 10 books back to your desk,

instead of going back to library 10 times