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Intel Core i7-875K and i5-655K - The Overclocking Club

By Vincent Chang - 28 Jun 2010

Overclocking

Overclocking

Everyone's attention for these K-series processors is obviously on its unlocked multiplier, so for our overclocking segment, we tried to see how far we could push the multiplier. Hence, we left the base clock untouched and just ramped up the multiplier and if needed, the voltages. We also disabled Turbo Boost so that we could get the maximum possible that all the cores could sustain. From the start, it was clear that one could push the multiplier up easily by a decent amount. It also emerged, which is perhaps not too surprising, that the dual-core Core i5-655K had the higher clock frequency at the end. 

The maximum overclock (multiplier only) on the Core i5-655K.

For the Core i7-875K, we hit the limits at a multiplier of 32 (4.25GHz), which is 10 steps more than the default 22x (which gives it a base CPU clock of 2.93GHz). For the Core i5-655K, the final multiplier was 34, (culminating at 4.5GHz) compared to its initial 24x multiplier (which gives it a base CPU clock of 3.2GHz). As you can see below, the higher clocks made quite the difference for CPU bound benchmarks like Cinebench and Vantage's CPU score. In Far Cry 2 however, we saw the overclocked Core i5-655K showing a 12% improvement, but there was barely any difference when it came to the Core i7-875K despite its increase in clock frequencies. In any case, for a raw increase in CPU performance for applications like video encoding, the extra and free clock speed will be very useful.

Overall, we were quite pleased with the amount of overclock we managed with air-cooling and a modest increase in voltage. If you're just trying a slight overclock, it's simply a matter of pushing up the multiplier and most users who know how to get into the BIOS should be able to do that. If not, Intel has provided a Windows based Control Center utility to tweak the core clock, voltages, and even the Turbo Boost multiplier limits for different number of cores. Do bear in mind that this amount of overclock may not be achievable with a stock cooler and you'll need an after-market cooler to get the best out of these K-SKU processors.

 

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