, a physical address
, also real address
, or binary address
, is the memory address
that is electronically (in the form of binary number
) presented on the computer address bus
circuitry in order to enable the data bus
to access a particular
storage cell of main memory
In a computer with virtual memory, the term physical address is used mostly to differentiate from a virtual address. In particular, in computers utilizing memory management unit (MMU) to translate memory addresses, the virtual and physical address refer to address before and after MMU translation, respectively.
In networking, physical address is sometimes a synonym of MAC address. The address is actually used on network's data link layer, not on physical layer, as the name would suggest.
Note: There are two basic types of physical addresses when referencing Ethernet which are large and fixed physical addresses and proNET, which has small relatively easy to configure addresses.
Depending upon its underlying computer architecture
, the performance of a computer may be hindered by unaligned
access to memory. As an example, a 16 bit computer with a 16 bit memory data bus such as an Intel 8086
generally works most efficiently 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 a data bus. Obviously, if the 16 bit data value starts at an odd address, the processor may actually need to perform two memory read cycles to load the value into it, i.e. one for the low address (throwing half of it away) and then a second to load the high address (again throwing half of the retrieved data away).