Storage Hierarchy

A typical computer has several different levels of storage. Each level of storage has a different speed, cost, and size. The levels form a storage hierarchy, in which the topmost levels (those nearest the processor) are fastest, most expensive and smallest.

Levels typically include processor registers, possibly some levels of cache(1), main memory, and possibly some levels of backing store.

Each level is commonly used as a cache(2) for the next level. For instance, virtual memory systems use main memory as a cache for backing store.

MORE EXPENSIVE / FASTER / SMALLER

| CENTRAL PROCESSING UNIT
| – Functional Units
| | PHYSICAL MEMORY
|Registers
| |Internal Cache
| – External Cache
| – Main Memory
– Backing Store

CHEAP / SLOW / LARGE