Computer Motherboard and Computer Science.

Computer Motherboard

Motherboard: A motherboard (sometimes alternatively known as the mainboard, main circuit board, system board, baseboard, planar board, or logic board,[1] or colloquially, a mobo) is the main printed circuit board (PCB) found in general-purpose computers and other expandable systems. It holds, and allows, communication between many of the crucial electronic components of a system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals. Unlike a backplane, a motherboard usually contains significant sub-systems such as the central processor, the chipset's input/output and memory controllers, interface connectors, and other components integrated for general purpose use and applications.

Motherboard specifically refers to a PCB with expansion capability and as the name suggests, this board is often referred to as the "mother" of all components attached to it, which often include peripherals, interface cards, and daughtercards: sound cards, video cards, network cards, hard drives, or other forms of persistent storage; TV tuner cards, cards providing extra USB or FireWire slots and a variety of other custom components.

Similarly, the term mainboard is applied to devices with a single board and no additional expansions or capability, such as controlling boards in laser printers, televisions, washing machines, mobile phones and other embedded systems with limited expansion abilities.



History: Prior to the invention of the microprocessor, the digital computer consisted of multiple printed circuit boards in a card-cage case with components connected by a backplane, a set of interconnected sockets. In very old designs, copper wires were the discrete connections between card connector pins, but printed circuit boards soon became the standard practice. The Central Processing Unit (CPU), memory, and peripherals were housed on individually printed circuit boards, which were plugged into the backplane. The ubiquitous S-100 bus of the 1970s is an example of this type of backplane system.

The most popular computers of the 1980s such as the Apple II and IBM PC had published schematic diagrams and other documentation that permitted rapid reverse-engineering and third-party replacement motherboards. Usually intended for building new computers compatible with the exemplars, many motherboards offered additional performance or other features and were used to upgrade the manufacturer's original equipment.

During the late 1980s and early 1990s, it became economical to move an increasing number of peripheral functions onto the motherboard. In the late 1980s, personal computer motherboards began to include single ICs (also called Super I/O chips) capable of supporting a set of low-speed peripherals: keyboard, mouse, floppy disk drive, serial ports, and parallel ports. By the late 1990s, many personal computer motherboards included consumer-grade embedded audio, video, storage, and networking functions without the need for any expansion cards at all; higher-end systems for 3D gaming and computer graphics typically retained only the graphics card as a separate component. Business PCs, workstations, and servers were more likely to need expansion cards, either for more robust functions or for higher speeds; those systems often had fewer embedded components.

Laptop and notebook computers that were developed in the 1990s integrated the most common peripherals. This even included motherboards with no upgradeable components, a trend that would continue as smaller systems were introduced after the turn of the century (like the tablet computer and the netbook). Memory, processors, network controllers, power source, and storage would be integrated into some systems.



Design: A motherboard provides the electrical connections by which the other components of the system communicate. Unlike a backplane, it also contains the central processing unit and hosts other subsystems and devices.

A typical desktop computer has its microprocessor, main memory, and other essential components connected to the motherboard. Other components such as external storage, controllers for video display and sound, and peripheral devices may be attached to the motherboard as plug-in cards or via cables; in modern microcomputers, it is increasingly common to integrate some of these peripherals into the motherboard itself.

An important component of a motherboard is the microprocessor's supporting chipset, which provides the supporting interfaces between the CPU and the various buses and external components. This chipset determines, to an extent, the features and capabilities of the motherboard.

Modern motherboards include:

Sockets (or slots) in which one or more microprocessors may be installed. In the case of CPUs in ball grid array packages, such as the VIA C3, the CPU is directly soldered to the motherboard.[3]
Memory Slots into which the system's main memory is to be installed, typically in the form of DIMM modules containing DRAM chips
A chipset that forms an interface between the CPU's front-side bus, main memory, and peripheral buses
Non-volatile memory chips (usually Flash ROM in modern motherboards) containing the system's firmware or BIOS
A clock generator produces the system clock signal to synchronize the various components
Slots for expansion cards (the interface to the system via the buses supported by the chipset)
Power connectors, which receive electrical power from the computer power supply and distribute it to the CPU, chipset, main memory, and expansion cards. As of 2007, some graphics cards (e.g. GeForce 8 and Radeon R600) require more power than the motherboard can provide, and thus dedicated connectors have been introduced to attach them directly to the power supply.[4]
Connectors for hard drives, typically SATA only. Disk drives also connect to the power supply.
Additionally, nearly all motherboards include logic and connectors to support commonly used input devices, such as USB for mouse devices and keyboards. Early personal computers such as the Apple II or IBM PC included only this minimal peripheral support on the motherboard. Occasionally video interface hardware was also integrated into the motherboard; for example, on the Apple II and rarely on IBM-compatible computers such as the IBM PC Jr. Additional peripherals such as disk controllers and serial ports were provided as expansion cards.

Given the high thermal design power of high-speed computer CPUs and components, modern motherboards nearly always include heat sinks and mounting points for fans to dissipate excess heat.



Form factor: Motherboards are produced in a variety of sizes and shapes called computer form factors, some of which are specific to individual computer manufacturers. However, the motherboards used in IBM-compatible systems are designed to fit various case sizes. As of 2007, most desktop computer motherboards use the ATX standard form factor — even those found in Macintosh and Sun computers, which have not been built from commodity components. A case's motherboard and power supply unit (PSU) form factor must all match, though some smaller form factor motherboards of the same family will fit larger cases. For example, an ATX case will usually accommodate a microATX motherboard. Computers generally use highly integrated, miniaturized, and customized motherboards. This is one of the reasons that laptop computers are difficult to upgrade and expensive to repair. Often the failure of one laptop component requires the replacement of the entire motherboard, which is usually more expensive than a desktop motherboard


CPU sockets: A CPU socket (central processing unit) or slot is an electrical component that attaches to a Printed Circuit Board (PCB) and is designed to house a CPU (also called a microprocessor). It is a special type of integrated circuit socket designed for very high pin counts. A CPU socket provides many functions, including a physical structure to support the CPU, support for a heat sink, facilitating replacement (as well as reducing cost), and most importantly, forming an electrical interface both with the CPU and the PCB. CPU sockets on the motherboard can most often be found in most desktop and server computers (laptops typically use surface mount CPUs), particularly those based on the Intel x86 architecture. A CPU socket type and motherboard chipset must support the CPU series and speed.


Integrated peripherals: With the steadily declining costs and size of integrated circuits, it is now possible to include support for many peripherals on the motherboard. By combining many functions on one PCB, the physical size and total cost of the system may be reduced; highly integrated motherboards are thus especially popular in small form factors and budget computers.
Disk controllers for a floppy disk drive, up to 2 PATA drives, and up to 6 SATA drives (including RAID 0/1 support)
integrated graphics controller supporting 2D and 3D graphics, with VGA and TV output
an integrated sound card supporting 8-channel (7.1) audio and S/PDIF output
Ethernet network controller for connection to a LAN and to receive Internet
USB controller supporting up to 12 USB ports
IrDA controller for infrared data communication (e.g. with an IrDA-enabled cellular phone or printer)
Temperature, voltage, and fan-speed sensors allow the software to monitor the health of computer components.
Peripheral card slots: A typical motherboard will have a different number of connections depending on its standard and form factor.
A standard, modern ATX motherboard will typically have two or three PCI-Express 16x connections for a graphics card, one or two legacy PCI slots for various expansion cards, and one or two PCI-E 1x (which has superseded PCI). A standard EATX motherboard will have two to four PCI-E 16x connections for graphics cards, and a varying number of PCI and PCI-E 1x slots. It can sometimes also have a PCI-E 4x slot (will vary between brands and models).

Some motherboards have two or more PCI-E 16x slots, to allow more than 2 monitors without special hardware, or use a special graphics technology called SLI (for Nvidia) and Crossfire (for AMD). These allow 2 to 4 graphics cards to be linked together, to allow better performance in intensive graphical computing tasks, such as gaming, video editing, etc.



Temperature and reliability: Motherboards are generally air-cooled with heat sinks often mounted on larger chips, such as the Northbridge, in modern motherboards.[5] Insufficient or improper cooling can cause damage to the internal components of the computer, or cause it to crash. Passive cooling, or a single fan mounted on the power supply, was sufficient for many desktop computer CPUs until the late 1990s; since then, most have required CPU fans mounted on their heat sinks, due to rising clock speeds and power consumption. Most motherboards have connectors for additional computer fans and integrated temperature sensors to detect motherboard and CPU temperatures and controllable fan connectors which the BIOS or operating system can use to regulate.