Your computer's power supply may be one of the least thought about

components in your computer, but when it stops working correctly,

nothing will work.

The power supply keeps things in your computer running smoothly. When

they run well, you won't even think about them, but when things go

wrong, it can become very annoying.

The power supply doesn't just run the power to the different parts of

the computer. It needs to run different voltages to different parts,

and besides that, it has to deliver them within a very tight range set

out in the ATX standard.

Power supplies went through a phase of being extremely unreliable.

This is because the actual parts are very cheap and standard and the

profit margin in the power supply business is higher than almost any

other computer part. The flooding of the market with poor quality

power supplies led to lots of failures and complaints.

More recently, the problems in that sector have decreased, the general

quality and build of power supplies has increased to a level where

nearly any power supply will deliver what it claims it will and within

specs. Most, but not all.

As with computer monitors, power supplies are one part that does not

need to be upgraded very often. The only additions have come from SATA

specific power plugs and the additional P4 plug in recent years and

even those are not always necessary.

So what do you actually need from a power supply?

The most basic requirement is that its power output can match the

power needed by the components inside your computer. Each part has its

own requirement and its own maximums and minimums on what it needs.

The claimed maximum power for each voltage are added together to give

the power rating for the power supply.

The main power user in the computer is the CPU. Some Pentium 4

processors are known to gobble lots of power. Hard drives use some

power too, but no more than 10W each, optical drives even less. The

motherboard itself uses some too. The other major user of power are

graphics cards.

As graphics cards have become more powerful, and with the advent of

Graphical Processing Units (GPUs), which are like CPUs which are

dedicated to graphics work, and situated on the graphics card, they

can now use more power than a CPU. If you are running a very fast PCIe

graphics card or a pair of them, you will need more power.

At the most basic a 300W power supply will be more than enough for

most day to day use desktop computers, even if they have a small AGP

graphics card. Only get more than 300W if you know you need it, or

expect you will need it in the future after upgrades. 500W will more

than suffice for even the most demanding system with 2 graphics cards,

but it needs to be a reputable brand.

Enermax, Antec, Fortron and Seasonic are good names in the power

supply business, you will not go wrong with their products. Even

though there is a small price premium, the security in knowing that

nothing will go wrong is worth it. Another power supply I like is the

X-connect from Ultra. Each of the cables that come from the power

supply are removable, so only the ones you are using need to be in the

box. Very convenient and neat, as long as I don't lose the cables.

Pre-assembled computers are known for having the cheapest power

supplies in them. As no-one really checks the power supply when buying

they just put the minimum inside. These are usually fine, but will

often buckle under the load of extra upgrades you may make. Bear in

mind that you might have to upgrade the power supply when installing

those new, really cool graphics cards.

So, keep these things in mind...

• Stick to major brands

• 300W only unless particularly needed

• Functionality before looks