Motherboard

Introduction to motherboards
The primary component of a computer is the motherboard (sometimes called the "mainboard"). The motherboard is the hub which is used to connect all of the computer's essential components.



As its name suggests, the motherboard acts as a "parent" board, which takes the form of a large printed circuit with connectors for expansion cards, memory modules, the processor, etc.
Characteristics
There are several ways in which a motherboard can be characterised, in particular the following:
• The form factor,
• The chipset,
• the type of processor socket used,
• the input-output connectors.
Integrated components
The motherboard includes some on-board components, meaning that they are integrated into its printed circuitry:
• The chipset, a circuit which controls the majority of resources (including the bus interface with the processor, cache memory and random-access memory, expansion cards, etc.)
• The CMOS clock and battery,
• The BIOS,
• The system bus and the expansion bus.
What's more, recent motherboards generally include a number of onboard multimedia and networking devices which can be disabled:
• integrated network card;
• integrated graphics card;
• integrated sound card;
• upgraded hard drive controllers.
The processor socket
The processor (also called the microprocessor) is the computer's brain. It runs programs using a set of instructions. The processor is characterised by its frequency, the rate at which it executes instructions. This means that an 800 MHz processor can carry out 800 million operations per second.
The motherboard has a slot (sometimes several, for multi-processor motherboards) into which the processor is inserted, called the processor socket or slot.
• Slot: A rectangular connector into which the processor is mounted vertically.
• Socket: In addition to being the general term, it also refers more specifically to a square-shaped connector with many small connectors into which the processor is directly inserted.
Within these two large families, there are different versions used, depending on the type of processor. Whatever slot or socket is used, it is essential that the processor be inserted gently, so that none of its pins are bent (it has hundreds of them). To make inserting them easier, a concept called ZIF (Zero Insertion Force) has been created. ZIF sockets have a small lever, which, when lifted, allows the processor to be inserted without applying any pressure, and when lowered, it holds the processor in place.
The processor generally includes some sort of foolproof device, in the form of a notched corner or coloured markings, which must be aligned with the corresponding markings on the socket.

Since the processor releases heat, it is necessary to dissipate it, to keep the circuits from melting. This is why it is generally mounted atop a heat sink (sometimes called a cooler or radiator), which is made of a metal which conducts heat well (copper or aluminium) in order to increase the microprocessor's heat transfer surface. The heat sink includes a base in contact with the processor and fins in order to increase the heat transfer surface. A fan generally accompanies the cooler in order to improve air circulation around it and to improve the heat transfer. The unit also includes a fan which vents hot air from the case and let fresh air come in from outside.
Expansion slots
Expansion slots are compartments into which expansion cards can be inserted. These are cards which give the computer new features or increased performance. There are several types of slots:
• ISA slots (Industry Standard Architecture): For inserting ISA slots. The slowest ones are 16-bit.
• VLB slots (Vesa Local Bus): Bus formerly used for installing graphics cards.
• PCIslot (Peripheral Component InterConnect): used for connecting PCI cards, which are much faster than ISA cards and run on 32 bits
• AGP slot (Accelerated Graphic Port): A fast port for a graphics card.
• PCI Express slot (Peripheral Component InterConnect Express): Faster bus architecture than AGP and PCI buses.
• AMR slot (Audio Modem Riser): This type of slot is used for connecting mini-cards to PCs which are built for it.

The input-output connectors.
The motherboard has a certain number of input/output sockets found on the rear panel.

Most motherboards have the following connectors:
• A serial port, for connecting old peripherals;
• A parallel port, mainly for connecting old printers;
• USB ports (1.1, low-speed, or 2.0, high-speed), for connecting more recent peripherals;
• RJ45 connector (called LAN or ethernet port) used for connecting the computer to a network. It corresponds to a network card integrated into the motherboard;
• VGA connector (called SUB-D15), for connecting a monitor. This connector interfaces with the built-in graphics card;
• Audio plugs (Line-In, Line-Out and microphone), for connecting sound speakers or a hi-fi system, as well as a microphone. This connector interfaces with the built-in sound card;