Q. Is it safe to over-clock my PC?

I always understood that over-clocking your computer’s CPU could make it unstable and meant you needed noisy fans to cool it down, but I notice that several specialist audio PC manufacturers now say they routinely over-clock processors on their machines. So is it now a good idea to do this and, if it is, what sort of increase is going to be ‘safe’?

Jerry Philips, via email

SOS columnist Martin Walker replies: 

The simplest definition of over-clocking is probably ‘making your computer go faster for free’, but a more accurate description might be ‘forcing one or more of your computer components to run faster than the manufacturer intended’.

Anyone who lives in a house where the mains voltage is higher than normal will find that their light bulbs burn brighter but need replacing more often. So, in PC terms, pushing your computer components beyond their nominal speeds can shorten their life. The increased power requirements of over-clocked components mean a greater strain on your computer power supply, while your over-clocked CPU, RAM or graphics card will also generate more heat when forced to run faster, and may therefore have a shorter life.

As you mention, the most obvious way to counteract this increased heat dissipation is to beef up component cooling, which often means more noise from CPU and case fans. However, more importantly, as you gradually increase any component’s speed beyond the manufacturer’s specification, you may find your computer starts to crash randomly, occasionally shuts down due to over-heating, or that a component completely burns out and needs replacing.

There are two approaches to over-clocking. Some enthusiasts go for the ‘extreme’ variety, which generally means gradually pushing motherboard component speeds and internal voltages ever higher by tweaking various parameters in its BIOS (Basic Input/Output System) until the computer crashes or refuses to boot up at all, and then backing them off slightly. During this process you have to carefully monitor various component temperatures to make sure you don’t burn anything out. You also have to stress-test the computer at your extreme settings for at least several hours to ensure that it’s totally stable.

In my opinion, extreme over-clocking is akin to playing Russian roulette, which is perhaps acceptable for a gaming machine, but not wise for a music computer that you rely on to capture many hours of creativity. A more sensible approach is to opt for a conservative increase in clock speed rather than pushing a particular machine to its limits while, again, monitoring temperatures and stability. Such ‘sweet-spots’ can be determined by experience for each make and model of CPU, but can vary considerably, although some recent processors seem relatively happy being over-clocked by up to 50 percent.

Some mainstream PC manufacturers don’t test their computers at all, which means that they can pare prices to the bone, but is why a few machines inevitably end up dead on arrival, and may even be found to have missing components that prevent them being booted up at all.

However, specialist audio PC builders already perform extensive soak testing and temperature monitoring on each and every machine before it gets shipped to the customer, which places them in an ideal position to offer their customers a ‘sensible’ over-clocking option that provides increased performance without compromising stability or long-term reliability. Components are still being operated outside the manufacturer’s specification, but you should, nevertheless, get a guarantee to cover you in the event of any system problems.

Is over-clocking a good idea on your own DIY or mainstream PC? Well, you’re on your own if anything goes wrong, and any damage won’t be covered under the normal guarantee. It’s not worth the risk (however small) if you’re already content with your computer’s performance, or if you’re a software developer or reviewer who has to be certain that any bugs discovered are due to the products being tested, and not due to your computer operating beyond its recommended speed. However, for those prepared to dabble, it’s certainly possible to achieve modest performance boosts on many computers fairly easily, if you take care, and more significant ones if you’re prepared for greater heat and fan noise.

Published in SOS April 2010