The ultimate guide to overclocking

You'll see another figure called 'External clock', 'Front side bus' or 'FSB'. The CPU's speed is this multiplied by the, you guessed it, multiplier. More likely, however, you'll be tweaking the FSB. Bump it up by 10MHz increments, rebooting each time until you hit the point where Windows refuses to load. When that happens, you'll need to use the CMOS reset. This is either a small button or a moveable jumper that restores the BIOS to default settings. You'll need to refer to the mobo's manual to locate it.

Next re-overclock the bus to the highest speed you've proved works. To go higher than that, you'll need to tweak the volts, or vCore. This needs to be done by the tiniest amount possible, and you should know what others have established is a safe voltage for your processor. You may also need to lower RAM clockspeed to stop the raised FSB from making your memory fall over.


By contrast to all that farting about with CPUs, 3D card overclocking is incredibly simple. It's all done from within Windows, with no rebooting required, and in Vista you'll even find that the system will recover from an unsuccessful overclock without locking up or bluescreening. For an NVIDIA board, you want an app called nTune. It's an official NVIDIA tool – grab it from

Then you just need to head over to the NVIDIA Control Panel (there should be an option for it, if you right-click on your desktop) and click on 'adjust GPU settings' under 'Performance'. If you select 'Custom clock frequencies' you can alter the core bus and the memory bus. As always, do it by tiny increments (10MHz or so) to identify the exact speed ceiling. There's an option in the NV control panel called 'system stability', and there you can run a looped render test to check the card can cope with the speed hike.

ATI cards are similarly straightforward. Load up Cataylst Control Center, again by right-clicking on the desktop and selecting its name. When prompted, choose 'Advanced' rather than the 'Basic' mode. From the list of settings on the left, you want the bottom one – ATI Overdrive. The best option whether you're a first or a fourtieth timer at this is to click 'Run automated clock configuration utility.'

This will test the card's GPU and RAM at various different speeds, working out what's safe to run at. It'll take a little while, but once done you should notice that Overdrive's added a few extra MHz. Click 'Apply', then gun up a few games and give them a quick run.

Best of the rest

While the benefits of RAM overclocking are fairly minimal, it can sometimes win you an extra frame or two in game or unclog a bottleneck that's causing occasional system chug. It's vital to know the official speeds for your RAM before you tinker – if you don't know already, use free app CPU-Z (

And now to the BIOS; you're looking for an option to alter the DRAM clock or memory frequency, or whatever random nomenclature your mobo manufacturer has settled on. Try and push it up a notch, eg. 400MHz to 410MHz. Bear in mind that DDR/DDR2 effectively doubles its clockspeed, so your BIOS may report it as, say, 800MHz rather than 400.

The overclock may fail. In which case, you've several options. You could drop the memory's clockspeed and raise the FSB instead. Or you could increase the voltage the RAM draws. Look for something like 'DRAM voltage' or 'VDIMM' and increase it by the tiniest amount at a time. Just remember that's a real risk of frying your memory and possibly entire system if you go too far.

Alternatively, try a latency overclock instead. Look for 'latency or 'CAS' in the BIOS and try decreasing it by 0.5, eg. from 3.0 to 2.5. For a final, comedy overclock, there's your mouse. Yeah, really. While you can't increase your rodent's sensitivity, you can improve the rate at which it reports its actions to Windows.

Grab USB Rate app from There's four speeds listed, but aim for the third, 500Hz. If the mouse, or any other USB devices stop working, you'll need to reset the speed. Use a PS/2 keyboard, tab to the speed slider and use cursor keys to select something lower, then tab again until 'Apply' is selected.

Originally published in PC Format, Issue 219

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