Overclocking - Core i5 655K

Overclocking - Core i5 655K

We'll do two separate overclocking sessions, one for each of the processors of course. We start of with the 32nm dual-core Core i5 655K.

If you want to overclock, you need a steady basis. As such we gave eVGA a call to see if they had a beta BIOS available for their P55 based eVGA Classified 200 that supports both K series processors. EVGA is ready for these processors, pop in the latest BIOS and you are good to go with full control over the multiplier, the overclock results you will see today are thus based on the P55 eVGA Classified 200 as shown below.

Ever since we met the Nehalem family of processors and the Front Side Bus was officially annihilated, things tend to change a little in the overclocking department. Only a little though. It's a little weird but the concept remains the same. In the BIOS you'll find a 133 MHz register, labeled the base clock -- look at that as your 'FSB' to play around with. Of course, with a K series processor, things are much easier as they have unlocked multipliers.

Our advice, just play around (carefully) with CPU voltage and even on the stock air cooler you can achieve some pretty snazzy results. Don't be afraid to hit 1.3~1.4 Volts. We were able to overclock the Core i5 655K processor to 4.2 GHz on simple air cooling.

• Choose a processor multiplier (we chose 28)
• Increase processor voltage a little bit to 1.30 ~ 1.35v
• Lower QPI ratio one step
• Lower memory multiplier to maximum stable memory frequency
• Now increase CPU base frequency, we set it at 150 MHz

We boot into Windows without issues, lowering voltage below 1.3 volts makes the system unstable while stressed, so the end result was a stable 4.2 GHz.
When we stress the CPU cores with Prime 95, temperatures now rise to roughly 80 degrees C (178F) which really is high and also the maximum limit you want to go to, as such we stopped at this point. Now again, I can't stress this hard enough, this was done with a simple heatpipe cooler. With proper cooling (LCS) you can get much higher we believe.