Overclocking greatly varies due to what hardware is being used and who is doing the overclocking. Always remember that no two pieces of hardware will perform the same, so our results will differ from what you might be able to get.
With stock BIOS settings, the Athlon II X4 635 processor runs with a 200MHz bus speed and a x15.0 multiplier that is used to reach the final core clock of 3.0GHz. The multiplier is locked, so the only way to overclock the processor is to raise the bus speed.
By cranking the voltage up to 1.575V in the motherboard’s BIOS we were able to get the FSB up to 255MHz and the system to an overclock of 3825MHz. It took a lot more voltage to hit this overclock than I like but it was a fairly stable set-up. We were able to hit a little higher overclock with the AMD Athlon II X4 640 than the Athlon II X4 635 that we reviewed a few months back, but not by much — only ~90MHz. It was achieved at a lower voltage, though.
The ASRock 890GX Extreme3 motherboard that we used for testing had a fairly decent BIOS that allows you to overclock a processor like the Athlon II X4 635 quickly and easily. The picture above shows the BIOS settings that we used to reach our highest overclock in case you have this board and processor combination and want to try to reach this level of performance.
With a quick look at the voltages we used you can tell we only needed to adjust the values on two of the settings to reach this overclock. It was really that simple. To go beyond an overclock like this you will need better cooling and you will need to spend more time fine tuning the voltages to get the most from your processor.
Above you can see the before and after results in 3dMark Vantage; the overclock did help overall system performance. After a 27.5% boost in the speed of the CPU we noticed a boost in the overall score of ~1100 3dMarks, but what was more impressive was the 2,100 3dMark boost in the CPU score! Overall, not a bad overclock on a budget oriented processor.
We should also point out that the AMD Athlon II X4 630 processor that we reviewed back in September 2009 was able to reach 3.85GHz with 1.55V. It would appear that the AMD Athlon II X4 series can get to roughly 3.8GHz with a little work and a good overclocking motherboard as we’ve had a few of them up at this clock frequency now on just air cooling.