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This article is about computer memory addressing. For the meaning in networking, see MAC 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 storage cell of main memory, or a register of memory mapped I/O device.

Use by central processing unit[edit]

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.[1]

Unaligned addressing[edit]

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 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 a data bus.[2][3]

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). In fact, on some architectures (such as the Motorola 68000 family), unaligned memory accesses will result in an exception being raised (usually resulting in a software exception being raised like POSIX's SIGBUS).[2]

Use by other devices[edit]

The direct memory access (DMA) feature allows other devices in the mother board but CPU to address the main memory. Such devices, therefore, also need to have a knowledge of physical addresses.

See also[edit]


  1. ^ Frank
 Uyeda (2009). "Lecture
Management" (PDF). CSE
Systems. UC San Diego. Retrieved 2013-12-04. 
  2. ^ a b Daniel Drake (2007-12-04). "Memory access and alignment". LWN.net. Retrieved 2013-12-04. 
  3. ^ Daniel Drake; Johannes Berg. "Documentation/unaligned-memory-access.txt". kernel.org. Retrieved 2013-12-04. 

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MediaPost Communications
Fri, 01 Aug 2014 10:15:00 -0700

Other identifiers such as full name, credit card numbers, social security numbers and license plate numbers are also referred to as PII because they can often be directly connected to phone number, email or physical address. Thus identifiers which are ...
Thu, 31 Jul 2014 16:35:28 -0700

All records or other information regarding the identification of the account, to include full name, physical address, telephone numbers and other identifiers, records of session times and durations, the date on which the account was created, the length ...
Fri, 01 Aug 2014 08:53:55 -0700

A lot of those common apps we use every day may expose PII [personal identifiable information], ranging from GPS or your physical address to a phone number to an actual address and other sensitive information you may have stored on the device.
Thu, 31 Jul 2014 22:37:30 -0700

They also are required to present proof of residence/physical address and immunization records. Elementary registration is from 8 a.m. to 3:30 p.m. Monday through Aug. 8 at the respective elementary schools. Returning students are not required to ...

Free Press Journal

Free Press Journal
Thu, 31 Jul 2014 21:29:18 -0700

The police will carry out the physical, address and criminal antecedent verification in seven days' time. After the verification is completed, the police station will then have to submit a report to the Special Branch (SB) II, CID in physical format ...
Business 2 Community
Tue, 29 Jul 2014 20:11:15 -0700

A physical gift is the best option to go for especially if you are in the business of direct mail. This is due to the fact that you need to give a valid reason for people to give you a physical address. It is also important to understand that ...
The Times-Picayune
Thu, 31 Jul 2014 13:26:15 -0700

As sheer coincidence, the first season will be staged in the 6,000 square foot Spitzfaden Community Center, with a physical address that offers a nomenclature dovetail: 3090 E. Causeway Blvd, Mandeville. Although the group hopes to move into a ...
Sioux Falls Argus Leader
Tue, 29 Jul 2014 21:41:15 -0700

Make sure to include the business' physical address and phone number on your website so potential customers know how to find you or reach you if needed. If your company has office space, include a photograph of the building to show that your company ...

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