Physical address

Representation of a memory address Diagram of relationship between the virtual and physical address spaces In computing, a physical address (also real address, or binary address), is a memory address that is represented in the form of a binary number on the address bus circuitry in order to enable the data bus to access a particular item (byte, word, etc.) of main memory, or a register of memory-mapped I/O device. Use by central processing unit In a computer supporting virtual memory, the term physical address is used mostly to differentiate from a virtual address. In particular, in computers utilizing a memory management unit (MMU) to translate memory addresses, the virtual and physical addresses refer to an address before and after translation performed by the MMU, respectively. Unaligned addressing Depending upon its underlying computer architecture, the performance of a computer may be hindered by unaligned access to memory. For example, a 16-bit computer with a 16-bit memory data bus, such as Intel 8086, generally has less overhead if the access is aligned to an even address. In that case fetching one 16-bit value requires a single memory read operation, a single transfer over