Memory controller

The memory controller is a digital circuit that manages the flow of data going to and from the computer's main memory. A memory controller can be a separate chip or integrated into another chip, such as being placed on the same die or as an integral part of a microprocessor; in the latter case, it is usually called an integrated memory controller (IMC). A memory controller is sometimes also called a memory chip controller (MCC) or a memory controller unit (MCU).

History

Computers using Intel microprocessors have traditionally had a memory controller implemented on their motherboard's northbridge, but many modern microprocessors, such as DEC/Compaq's Alpha 21364, AMD's Athlon 64 and Opteron processors, IBM's POWER5, Sun Microsystems's UltraSPARC T1, and more recently Intel's Core i7 and Core i5 CPUs have an integrated memory controller (IMC) on the microprocessor in order to reduce memory latency.

While an integrated memory controller has the potential to increase the system's performance, it locks the microprocessor to a specific type (or types) of memory, forcing a redesign in order to support newer memory technologies. When DDR2 SDRAM was introduced, AMD released new Athlon 64 CPUs. These new models, with a DDR2 controller, use a different physical socket (known as Socket AM2), so that they will only fit in motherboards designed for the new type of RAM. When the memory controller is not on-die, the same CPU may be installed on a new motherboard, with an updated northbridge.

Memory

In psychology, memory is the process in which information is encoded, stored, and retrieved. Encoding allows information from the outside world to be sensed in the form of chemical and physical stimuli. In the first stage the information must be changed so that it may be put into the encoding process. Storage is the second memory stage or process. This entails that information is maintained over short periods of time. Finally the third process is the retrieval of information that has been stored. Such information must be located and returned to the consciousness. Some retrieval attempts may be effortless due to the type of information, and other attempts to remember stored information may be more demanding for various reasons.

From an information processing perspective there are three main stages in the formation and retrieval of memory:

Computer hardware

Computer Hardware (usually simply called 'hardware' when a computing context is concerned) is the collection of physical elements that constitutes a computer system. Computer hardware is the physical parts or components of a computer, such as the monitor, mouse, keyboard, computer data storage, hard disk drive (HDD), graphic cards, sound cards, memory (RAM), motherboard, and so on, all of which are physical objects that are tangible. In contrast, software is instructions that can be stored and run by hardware.

Software is any set of machine-readable instructions that directs a computer's processor to perform specific operations. A combination of hardware and software forms a usable computing system.

Von Neumann architecture

The template for all modern computers is the Von Neumann architecture, detailed in a 1945 paper by Hungarian mathematician John von Neumann. This describes a design architecture for an electronic digital computer with subdivisions of a processing unit consisting of an arithmetic logic unit and processor registers, a control unit containing an instruction register and program counter, a memory to store both data and instructions, external mass storage, and input and output mechanisms. The meaning of the term has evolved to mean a stored-program computer in which an instruction fetch and a data operation cannot occur at the same time because they share a common bus. This is referred to as the Von Neumann bottleneck and often limits the performance of the system.

Carnegie Mellon University

Coordinates: 40°26′36″N 79°56′37″W / 40.443322°N 79.943583°W / 40.443322; -79.943583

Carnegie Mellon University (Carnegie Mellon or CMU; /ˈkɑːrnᵻɡi ˈmɛlən/ or /kɑːrˈneɪɡi ˈmɛlən/) is a private research university in Pittsburgh, Pennsylvania.

The university began as the Carnegie Technical Schools, founded by Andrew Carnegie in 1900. In 1912, the school became the Carnegie Institute of Technology and began granting four-year degrees. In 1967, the Carnegie Institute of Technology merged with the Mellon Institute of Industrial Research to form Carnegie Mellon University. The university's 140-acre (57 ha) main campus is 3 miles (4.8 km) from Downtown Pittsburgh and abuts the Carnegie Museums of Pittsburgh, the main branch of the Carnegie Library of Pittsburgh, the Carnegie Music Hall, Schenley Park, Phipps Conservatory and Botanical Gardens, the Pittsburgh Golf Club, and the campus of the University of Pittsburgh in the city's Oakland and Squirrel Hill neighborhoods, partially extending into Shadyside.