A new processor can give your system a new lease of life, but how do you pick which CPU to upgrade to?

CPUs are fairly easy to upgrade in theory, but buying the newest model available often means a complete reworking of your current machine. It's all very well recognising how powerful the Intel Core i7 X980 is, but you won't be able to just drop it into your Phenom rig and hope for the best.

There are two ways of tackling a potential processor upgrade, and both have pros and cons. The first is to replace your current processor with the fastest pin-compatible option currently out there. This is the most affordable type of CPU upgrade, as you can generally get away with buying the best original equipment manufacturer (OEM) model and simply replacing your current chip like-for-like.

Unfortunately this usually only results in a small speed boost, unless you are making the jump from a dual-core chip up to a three-or four-core offering.

AMD's decision to focus on a single socket for its desktop processors means its chips are easier to upgrade, as there are some fairly large upgrades available that use the same packaging. Visit your motherboard manufacturer's site to see whether your existing board supports the CPU you are looking at, or if there is a BIOS update that will add support for that chip before buying.

You'll need to bear in mind that if the new chip supports DDR3 and your motherboard only has DDR2 sockets, then you will be limited to using the older standard. If your motherboard has both types of memory slot present, upgrade the RAM for a further boost.

Screw the expense

The second option generally means that you ignore your existing hardware and simply go for the best processor available, picking up the requisite motherboard, memory and possibly graphics card as needed. This option is generally constrained by expense, because replacing multiple components is always going to be costly.

It will however result in the biggest performance boost to your system – especially if you use multi-threaded applications and are making the move to a multicore processor.

Upgrading your CPU can also mean that you need a new cooler, which is another potential expense, unless you pick a retail CPU that includes a compatible fan. If a pin-compatible CPU exists that will give your system a large performance boost then we would recommend you go with that, otherwise upgrading to the likes of the Core i5 is the sensible choice.

How to: Upgrade your CPU

1. Flash the BIOS

CPU upgrade 1

We'll assume that your motherboard needs a BIOS update before you can use your new CPU. Manufacturers provide updates in different ways, but all modern boards generally support flashing the BIOS from within Windows.

We would first recommend scouting the forums to make sure people aren't having problems with the latest BIOS. If you haven't updated for a while, you may need to install a string of them, but the general process is the same: flash the BIOS, reset to the defaults and check for updates. Rinse and repeat.

2. Remove the existing CPU

CPU upgrade 2

Before removing your CPU, benchmark your machine so you can see how much of a difference you've bought yourself. Synthetic benchmarks such as the X.264 video encoding test are particularly useful for comparing multithreaded upgrades.

Once you have figures to compare, power off your machine and give it a minute or two to cool. Unclip the processor's cooler, unplug the fan's power cable and ease it out of the way. Lift the lever holding the CPU in place and then pull the component free from the motherboard.

3. Install the new processor

CPU upgrade 3

If you've bought a retail CPU package, you can discard your old cooler because your new chip will have one that is designed for its thermal envelope.

Remove the chip from the packaging and ease it into the socket. Make sure that the chip is orientated correctly by lining up the lugs.

Add a little thermal paste to the top of the CPU and then place the cooler on top and clip it into place, wiggling the cooler first to make sure the grease is spread evenly. Connect the fan power cable, restart your PC and you're done.