Getting to know your motherboard

The motherboard may not be the most talked about component inside a PC but it's certainly the most important.

The motherboard (or 'mainboard' or even just 'mobo') is a large circuit board covered with chips, sockets and silver circuit trails. It's usually screwed in place to one side of a PC's case, with sockets poking out of slots at the back. Cables connect the motherboard to other devices - wide, flat, grey cables for the disk drives and coloured cables to the power supply.

The motherboard isn't designed to be easily removed - once it's in there, it only needs to come out if there's a fault. Thanks to the PC's modular design though, replacing a motherboard is still a simple task, if not a quick one.

Most PC users encounter the motherboard when they're plugging something new into it; whether it's more memory or an expansion card. There are special slots on the motherboard for this purpose and different makes of motherboard differ in the number and type of slots they provide. All motherboards have a connection for the processor too, either in the form of a square socket or a rectangular slot, depending on the type of processor they are designed for.

All motherboards also have a 'chipset' - a collection of electronics that control its basic functions. A chipset doesn't have to be made by the same company as the motherboard but you can't buy one without the other. Some chipsets also incorporate more sophisticated functions, such as sound and graphics.

The reason for this is price - a PC with a motherboard that has built-in functions can be sold at a lower price than one that needs dedicated sound and graphics cards. The knock-on effect is that if AGP graphics are built into a motherboard, there's no need for a separate AGP expansion slot, which means there is no way to upgrade the PC's graphics to keep pace with new games.

The basics

Every device in a computer connects to and communicates through the motherboard. There are slots for memory modules, connections for disk drives, sockets for a mouse and keyboard, and so on. No matter what you plug into a computer, be it inside or out, it ultimately connects to the motherboard.

All devices communicate with each other through a motherboard over the 'bus'. The bus is a little like a road along which devices send their data 'traffic'. Each type of connection in a computer has its own bus - there's a processor bus, a USB bus, a serial bus, and so on. Each bus operates at different speeds and there are electronics that control the flow of data (the chipset) to prevent 'jams'.

The most commonly mentioned buses in a PC are those used for expansion cards and there are three types. The oldest - the ISA bus - has now all but been replaced by the faster PCI bus for connecting such things as modems and sound cards. Graphics cards also have their own very fast bus called AGP. For a handy comparison, think of these buses as the A-road, motorway and autobahn of your motherboard.

The science

All motherboards fall broadly into a category based on their design. Early motherboards were 'AT' motherboards (named after the IBM AT PC they were used in) but these were replaced when the Pentium II processor was launched by the more efficient ATX motherboard and the smaller Micro ATX motherboard.

Each motherboard design requires a specific PC case (an AT, ATX or Micro ATX case) that has mounting brackets and socket holes in the appropriate places.

ATX motherboards are still the most common type and there are different models for different processors - some have slots for Pentium II and older Pentium III processors, some have sockets for new Pentium III and Pentium 4s and some are for use with AMD processors.

The chipset used on a motherboard can affect its performance and some manufacturers are preferred to others for this reason. Some motherboards are also more 'tweakable' than others.

Motherboards that use jumpers for their configuration can have their performance boosted by using 'incorrect' settings - a risky process known as 'overclocking'.

Why you need to know about it

Few PC manufacturers state what make of motherboard is in their PCs and those that do usually don't give you a choice. This isn't really a big deal; after all, do you buy a car on the strength of its gearbox?

Knowing a few things about the motherboard you're getting in a new PC can be useful though, and if you're building your own system from scratch, it's essential. The most important aspects are what processors it supports, how many free expansion and memory slots there are and what kind of memory it uses. Once you know the motherboard make and model, head straight to its manufacturer's website and get the low-down.

If you're brave enough, you can even browse some motherboard reviews at sites such as www.tomshardware.com but be warned - you might need a boffin on hand to translate the information you get into English.

JARGON BUSTER:

AGP: Accelerated Graphics Port. A PC interface for super-fast 3D graphics.

Expansion card: Card that can be fitted in an expansion slot within your PC to enhance its capabilities.

Jumper: Little metal pins, found on expansion cards and motherboards, for changing settings manually.

PCI: Peripheral Component Interconnect. A high-performance expansion slot for desktop PCs.