Primary storage

Primary

Primary storage, including ROM, EEPROM, NOR flash, and RAM, is usually byte-addressable. Such memory is directly or indirectly connected to the central processing unit via a memory bus, comprising an address bus and a data bus. The CPU firstly sends a number called the memory address through the address bus that indicates the desired location of data. Then it reads or writes the data in the memory cells using the data bus. Additionally, a memory management unit (MMU) is a small device between CPU and RAM recalculating the actual memory address. Memory management units allow for memory management; they may, for example, provide an abstraction of virtual memory or other tasks.