Computer Components - The Motherboard Explained

Published: 18th November 2010
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The term "motherboard" or "mainboard" refers to the most important component found inside a personal computer or PC. It is a large circuit board mounted to one side or bottom of the computer case depending on the type of PC. Even laptops contain a motherboard but these are designed specifically for the laptop in which they are fitted. There are several types of motherboard and they are categorized by the type of case they fit into also known as the form factor. ATX and mATX or micro ATX are the two most common types installed in most modern PCs.

The motherboard's role is to allow everything to communicate with each other. The circuit board contains a number of ports or connectors allowing the various internal components within the computer to communicate with the processor, memory etc. All of these connectors have a role and allow various components and devices to be fitted or installed internally or externally.

In the rest of this article I will explain the function of each of these ports or connectors and the devices that may be connected to them.

CPU or Processor Socket

The CPU socket is rather self explanatory as it holds the CPU. There are various types of processor available and each is designed to fit a certain CPU socket type. The socket is designed so that the processor can only be fitted one way. This is usually determined by a series of notches cut out of the edges of the CPU. These notches will match the CPU socket for correct installation of the processor. The motherboard CPU socket usually contains a mechanism or latch to firmly lock the processor securely into the socket.

Memory Slots

Again the memory slots are just that. They hold the computer memory in place. Motherboards can have a varying amount of memory slots fitted to them. In most home PCs there are two, three or four slots. As with the CPU socket, the memory slots are designed to hold specific types of memory. The slots have a number of raised points designed to correspond with the correct type of memory module, they also help to determine the orientation of the memory when installed. At each end of the slot a small latch device can be found. These latches are opened before installing the memory module and lock it in place as the module is inserted into the slot.

SATA Connectors

These connectors allow devices such as hard disk drives and CD/DVD drives to be installed in the computer. The amount of these connectors varies depending on the motherboard. The connector can be recognised by the small L-shaped receptacle which prevents improper fitting of the SATA cables.

IDE/PATA Connectors

These are the older type of connection for hard disk drives and CD/DVD drives. Older motherboards may have two of these connectors, a primary and secondary. An IDE cable would be used to connect up to two devices to each connector. The connector has two rows of pins and a notch cut out of one side enabling easy fitting of the cables ensuring that they are correctly fitted. Modern motherboards may only have one IDE connector fitted to allow either an older hard disk or CD/DVD drive to be installed.

AGP Graphics Slot

This is a brown coloured slot used to fit the older AGP graphics cards. On some motherboards this would have a small latch at one end to securely hold the graphics card in place.

PCI, PCI-E Expansion Card Slots

These are usually white in colour and the number can vary dependant on the motherboard. The older PCI has now been replaced by the PCI-E or PCI Express standard. They allow expansion cards such as sound, network or multimedia cards to be installed allowing easy expansion of the computers functionality. Fitting a card simply involves pushing the expansion card into the slot when the computer is powered off.

Motherboard Header Connectors

The motherboard contains a series of small connectors in various locations around the board. They usually consist of a number of raised pins. These header connectors have a variety of uses. Some allow USB ports located on the case to be connected, others are for connecting the front panel audio connections such as headphone and microphone sockets housed on the computer case. Connecting to these headers can be awkward and consultation of a motherboard manual is usually required.

External Ports

On the rear facing edge of the motherboard there are a number of ports that are visible on the rear of the PC. These may vary depending on the age of the board. The common ports are PS2 which are coloured purple for connecting a keyboard, green for connecting a mouse. There may also be a red parallel printer port although these are rarely found on modern boards. Another port which is less common on modern boards is the turquoise serial connectors that are used to connect a variety of devices such as old moderns, bar code scanners etc. Some motherboards may have a network or RJ45 port used for connecting the computer to a network but this is not always present. USB and Audio connection ports are also located on the rear of the board allowing external USB devices and speaker systems or microphones to be connected to the PC.



As we can see above the motherboard is the centre piece when it comes to connecting all the various computer components inside and outside of the PC. So how does the motherboard control all these devices and allow them to communicate successfully?

On the motherboard there is sometimes one or two micro-chips which control the motherboard functions. They are sometimes known as the chipset but the correct names are "Northbridge" and "Southbridge" chipsets. Each has a specific role for controlling various communication functions between the various components connected to the motherboard.

The author has worked in the IT industry for approximately 15 years and has worked in various support roles for companies and public bodies. The company for which he is now employed IvoryEgg.com is an online supplier of motherboards in the UK. He also writes for the company blog IvoryBlog.



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