PC System Board

When you take off the cover of your PC computer, you become exposed to a number of circuit boards and all that other stuff - it might be confusing, no doubt. Lets take a closer look at the biggest and perhaps one of the most important elements of a computer - its motherboard.

Motherboard is the main circuit board in the computer; you can easily spot it.

1.	Ports	7.	Power connector
2.	ISA Slot	8.	Memory sockets
3.	PCI Slots	9.	I/O connectors
4.	AGP Slot	10.	Battery
5.	CPU Slot	11.	Chipset (Southbridge)
6.	Chipset (Northbridge)	12.	BIOS chip

A motherboard contains a number of elements vital for the operation of your computer. Following is a description of these elements:

• Connectors - devices used to connect various components to the motherboard. There are two basic types of connectors - male and female connectors. Male connectors contain exposed pins, while female ones contain holes where male connectors can be inserted.

• Expansion slots - special kinds of female connectors on the motherboard where the additional circuit boards are inserted to add more functions to your computer. There are several types of slots used in modern computers:

  • PCI (Peripheral Component Interconnect) - a peripheral bus slot used to provide the high-speed data path between CPU and peripheral devices such as video controllers, network controllers, etc. There are typically three or four PCI slots on the motherboard. The PCI is the second shortest slot on the motherboard after the ISA slot which is the longest. The PCI slots are usually white.

  • AGP (Accelerated Graphics Port) - a special slot located about an inch farther back from the PCI slot. AGP specification is designed to increase the speed of 3D graphics because it provides direct connections between the graphics controller and main memory. Usually, there is only one AGP slot on the motherboard and it is brown. It is the shortest slot on the motherboard.

  • ISA (Industry Standard Architecture) - an expansion slot used to accept video, audio and other cards, just like the PCI slot. Usually motherboards have a combination of ISA and PCI slots because the ISA and PCI buses are currently used on most of the motherboards to connect CPU (processor) and peripheral devices. However, it is expected that the ISA will be eliminated within the year 2000. The ISA slots are black and the longest ones.

• Expansion boards - circuit boards inserted into the expansion slots to add some capabilities to your computer, for example, video controllers, audio controllers, disk controllers, etc. Nowadays the support for various devices can be built into the motherboard. For example, if the specification for your motherboard reads "with VGA adapter on-board", it means that you will not have to add the additional board to connect your monitor; the card is already contained in the microchip on the motherboard.

• CPU (Central Processing Unit) is the "brains" of the computer. It is usually referred to as a processor. Processors come in various sizes but you can easily spot it - it is the biggest chip on the motherboard with the cooler on top of it. Most calculations take place in CPU.

• BIOS (Basic Input/Output system) - it is physically represented by a small chip on the motherboard. BIOS is the lowest level software contained in the chip on the motherboard and retained there even when you turn the power off. It acts as an interface between the hardware and the operating system on your computer. It allows you to control the hardware settings of your computer; it is also responsible for the boot-up when you turn on the computer, and a number of other system functions.

• Memory (also referred to as RAM - Random Access Memory). Memory, in this context, means the temporary storage of data in the chips. You can see slots for the memory chips on the motherboard. There are four of them, usually. Currently, there are two main types of memory chips used in personal computers - SIMM (Single In-line Memory Module) and DIMM (Dual In-line Memory Module). RAM data is retained only when the computer is on; once off, all data is erased.

• Ports - are sockets used to connect external devices, such as a modem, a printer, a mouse, a scanner, etc. to a computer. There are two main types of ports - serial (or communication) ports (9 and 25 pins, male) and parallel ports (25 pins, female). Ports can be located on the extension board or incorporated into the motherboard.

• Controllers - the devices that control the transfer of data from computer to a peripheral device and the other way around. Peripheral devices are hard disks, monitors, printers etc. Controllers are single chips. When you buy a computer, it should be equipped with all necessary controllers either on-board or on expansion boards. However, if you decide to attach additional devices, you may need to install additional controllers that come on expansion boards.

All functions mentioned above are performed by chips - microminiaturized, electronic circuits, which reside on the motherboard and make up the so-called motherboard chipset.