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Overclock your PC hardware

Posted on 11 Feb 2009 at 12:37

Once officially frowned upon, overclocking is now very much an accepted way of getting more performance out of hardware, and especially getting more bang-per-buck by using cheap mid-range components and upping their frequency to match or exceed the level of high-end parts. Certain processors and hardware are better than others, and some become legendary. Probably the best example in recent years has been Intel's quad-core Q6600 processor, which can often easily be taken to 3GHz and beyond, even though its rated speed is only 2.4GHz. In fact, the advent of Intel's Core and Core 2 processors heralded a new era of easy overclocking. The 45nm parts run so cool in general use that overheating is hardly a problem at all, meaning you can continue to use a stock heatsink while pushing the processor way beyond its rated speeds.

For overclocking your existing hardware on a zero budget, the ideal platform is a clock-unlocked processor. This means one that allows its clock multiplier to be altered via the PC's BIOS. The basic front-side bus clock signal - the signal that allows the motherboard and its components to work together - is generated by the motherboard. That signal is multiplied so that the processor can run at its much higher frequencies, while remaining in sync with the rest of the system. A clock-unlocked processor allows this multiplier ratio to be set in the BIOS, whereas clock-locked versions can only be indirectly overclocked by upping the front-side bus speed.

The essential technique for overclocking is simple, but time-consuming. It's essentially an iterative process: boot into the BIOS and increase front-side bus or CPU multiplier frequency (or both) a little, test for stability; increase a little more; test for stability, and so on. At some point, clock speeds will get too high and the system will become unstable.

The potentially frustrating part is that this can manifest itself in a number of ways. The system may completely refuse to POST: in other words, the power-on self-test will fail and you won't even get to the BIOS start-up screen or the "happy beep" that indicates a healthy PC powering up. But it may get halfway through booting Windows and then crash with a "Blue Screen of Death" error message, or simply stop responding and just hang. If you do manage to boot into Windows, you still aren't out of the woods. The PC may seem fine, but as soon as you stress the processor the extra power dissipated by the faster clock frequency can mean the processor overheats, or you'll get random software errors, an unexpected reboot, a system hang, or various combinations of all three.

You should only deem an overclock successful once you've soak-tested the PC in its new configuration by running a CPU-intensive application for at least a few hours. The traditional tool for the soak test, believe it or not, is an old Windows 95 application called Prime95. It was originally written to look for Mersenne primes, which are special-case prime numbers. Download it from www.mersenne.org/freesoft.

Once you've downloaded the software, just run the prime95.exe file and you'll find a helpful dialog box with a button labelled Just Stress Testing. Selecting "In-place large FFTs" will give the CPU the maximum stress, which is what we want. In the "Number of torture test threads to run" box, enter the number of cores in your CPU; in other words, enter "2" for a dual-core CPU and "4" for a quad-core. Hit OK and wander off and do something else for an hour - your PC won't really be usable, because every core will be saturated by the Prime95 routines. If the machine is still working when you get back after an hour, you can consider the overclocked state to be a stable one.