Make your PC go faster for free

Posted on 3 Jul 2009 at 12:03

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Over the next few pages, we'll focus on the main option. We'll apply only mild adjustments to the PC's processor and graphics card to get an idea of how much more performance you're likely to see, even from relatively small changes.

If your system is fairly modern, the chances are that it will be suitable for overclocking. We'd recommend doing some further research on the subject to see what it might be capable of. And if you're considering an upgrade, don't open your wallet until you've overclocked your system - you could get the speed boost you want for free.

Overclocking: The downsides

There are a couple of disadvantages to overclocking. As you increase the frequencies of your hardware, you often need to increase the amount of voltage it uses, too. This doesn't mean you need an extra wall socket, though. The difference is usually less than half a volt, which is adjusted in your PC's BIOS (more of which later). The result is an increased heat output, which can require more capable cooling of the processor in particular. If you get this wrong, it's easy to make your system unstable.

As a rule of thumb, we'd advise not increasing any settings above 20 per cent of the default value unless you absolutely know what you're doing. This is especially true for voltages, which can actually damage your hardware. The following guides, which are based on an average, mid-range PC and tweak the processor and graphics card frequencies, will steer you safely through the process to a faster PC.

Overclocking basics

The speed of the processor and memory and the connection to other components such as the graphics card are all controlled by a single external bus speed. The speeds of other components are purely multiples of this speed.

For AMD processors, this external bus runs at 200MHz. For Intel Core i7 processors it runs at 133MHz and for older Intel processors it runs at 200MHz, 266MHz, 333MHz or 400MHz, depending on the model of the chip.

The processor's speed is determined by its multiplier. Our test PC has an Intel E5200 processor, which has a 12.5x multiplier and an external bus speed of 200MHz. This gives us a processor speed of 2.5GHz (in other words, 200MHz x 12.5). The same rules govern the speed of AMD and Core i7 processors.

The primary method for overclocking is to adjust the external bus speed. In our example, increasing the bus speed by 2MHz increases the processor's frequency by 25MHz (2 x 12.5). For most Intel processors, the BIOS setting may be called the FSB; for AMD processors it's probably called HTT; for Core i7 chips it could be called Base Clock.

The problem with this method is that increasing the external bus speed also increases the speed of other components that rely on it, including the memory.

The speed of DDR, DDR2 and DDR3 memory is quoted in MHz, such as 800MHz DDR2. This figure is achieved in two ways. First, the memory doubles the base frequency (DDR stands for Double Data Rate), so the real frequency of DDR2 800MHz memory is 400MHz (800MHz ? 2). This 'real' speed is determined by a multiplier (called a ratio in the BIOS) of the processor's external bus. Our Core 2 Duo E5200 has an external bus speed of 200MHz, so the memory ratio is 2:1 (2x): 200MHz x 2 = 400MHz.

If we increase the external bus by 20 per cent to 240MHz, the RAM's speed will therefore rocket to 960MHz. This is pushing its limits, and most RAM chips will probably fail at this speed. A failure in memory can cause a failure in operating system files, requiring Windows to be reinstalled. Before we talk about overclocking the processor, then, it's important that you understand how to prevent memory problems.