Question

Explain in detail the memory hierarchy with example

Answer 1

The memory system is a hierarchy of storage devices with different capacities, costs, and access times.

The idea centers on a fundamental property of computer programs known as locality. Programs with good locality tend to access the same set of data items over and over again, or they tend to access sets of nearby data items. Programs with good locality tend to access more data items from the upper levels of the memory hierarchy than programs with poor locality, and thus run faster. Figure 1 shows a typical memory hierarchy with relationship between the cost per bit, the access time and the hierarchy.

Memory hierarchies work because well-written programs tend to access the storage at any particular level more frequently than they access the storage at the next lower level. So the storage at the next level can have a larger access time, and thus will be larger in size and cheaper per bit.

The overall effect is a large pool of memory that costs as much as the cheap storage near the bottom of the hierarchy, but that serves data to programs at almost the rate of the fast storage near the top of the hierarchy.