How to build your own PC

The days when building your own PC meant making big savings over buying a ready-made computer are gone. It's now possible to buy a powerful yet affordable PC from your local supermarket. So why would anyone consider building their own computer?

Building a PC is an educational experience that gives a good idea of what each component looks like, how it fits into the computer and even what each sounds like. This can make it easier to diagnose problems or upgrade a PC at a later date. It can also be fun.

This Masterclass will provide help on choosing the important components of a modern PC.

The processor
The processor is the first buying decision, since it affects other aspects of the PC such as the motherboard and power supply, which we'll come to presently.

Two companies, AMD and Intel, essentially control the PC processor marketplace. Even the cheapest modern processor from either firm will be fast enough to cater for internet browsing and word-processing. Moreover, spending £1,000 on a top-end processor is no guarantee of a big speed boost over a £300 one - there are too many other factors at play.

That said, avoid Pentium 4 processors (Intel's last generation) and AMD's older Athlon X2 models found in bargain bins. These chips use more power than the current generation so any initial savings could be wiped out by higher electricity bills.

Modern processors tend to have more than one core and, in theory, the more cores a CPU has, the better the overall performance. The reality, though, is that a dual-core chip will suffice because few applications and games can make use of processors with four cores (called quad-core chips).

So, what should you buy? Well, we're going to avoid giving specific recommendations because this Masterclass is not a buying guide. Currently, Intel has the performance lead over AMD, with Intel's Core 2 Duo and Core 2 Quad being noticeably faster than AMD's Phenom chips. However, the Phenom processors are less expensive.

For our example, we'll use a Core 2 Duo E6750, running at 2.67GHz, but any modern processor will do. As a rule, the higher the frequency (the GHz number) the faster the processor. But this rule doesn't apply when comparing AMD with Intel processors or when comparing older generations of processors with newer ones (a 3.8GHz Pentium 4 is slower than a 2.67GHz Core 2 Duo).

Consider also power consumption. Each processor is listed with a TDP (thermal design power) figure. The higher this is the more energy it uses and the higher the environmental impact and electricity bill.

Shops will often list components in two variants: OEM and retail. OEM (original equipment manufacturer) products are designed for PC manufacturers and come with little packaging and accessories.

Retail products are more expensive but come with a well-presented box and often some software and hardware accessories. For the purpose of building a PC, it's often worth saving the cash and buying OEM products..

A retail processor will come with its own cooler (fan), but cheaper OEM chips won't. However, a CPU cooler is a necessity so when buying one, make sure it is compatible with the processor being used. Only a few processor fans include a thermal pad, but these are essential to ensure good contact between the processor and cooler. So, it's important to buy some processor thermal paste costing around £5.

The motherboard
The processor plugs into a motherboard, connecting it to all other parts of the PC. Mainstream motherboards support either AMD processors or Intel processors, but it's important to check a motherboard is compatible with the specific processor in use, since some do not support the fastest quad-core processors, for example.

Motherboards come in various sizes. The most common are microATX (mATX) and ATX. ATX is the bigger of the two and requires an ATX case to hold it. MicroATX motherboards are smaller and can fit into both mATX cases and bigger ATX cases.

MicroATX motherboards usually sacrifice some PCI slots to save space, so if lots of peripheral cards (such as sound cards, Wifi cards and TV tuners) are destined to be installed, it's worth buying an ATX motherboard.

The best way to decide which motherboard to buy is to make a list of the ports and slots needed (say, four USB ports, two Sata ports, one Firewire, two PCI slots etc) and then make sure the motherboard has everything listed. We've chosen an Asus P5E-VM HDMI mATX motherboard for our PC, which supports all the latest Intel processors. It has one PCI Express x16 slot for a graphics card but also includes integrated graphics and integrated audio,

Memory
The amount of random-access memory, sometimes called Ram, installed in a PC affects how many programs can be in use at the same time without the PC feeling sluggish. The most common versions of Windows XP and Windows Vista can't make use of more than 4GB memory and for most 2GB should be fine.

The two most common types of memory are DDR2 and DDR3. The latter is expensive and only usable on the fanciest, high-end motherboards.

The biggest factor governing memory performance is frequency (the MHz number). Ram rated at 667MHz, 800MHz or 1,066MHz will provide adequate performance (we've plumped for 2GB of 1,066MHz DDR2 memory). Only experienced users should buy memory that is rated beyond 1,066MHz, because the motherboard must be tweaked to use it

Hard disks and optical drives
Hard disks come with different speed ratings, ranging from 4,200 revolutions per minute (rpm) to 15,000rpm. A common speed is 7,200rpm, which offers the best value for money. We've chosen a Western Digital GP Caviar hard drive, with a 7,200rpm speed and 1TB of storage. This hard disk can vary its spin speed, slowing down when the PC isn't doing much to save energy.

For a desktop PC, a 3.5in hard disk is appropriate, but optical drives - a DVD drive, in other words - measure 5.25in. We chose a Pioneer BDR-202 Blu-ray writer that can play high-definition movies, as well as handling DVDs and CDs. Basic DVD writers are cheaper, often costing less than £20 and coming with useful burning software.