The use of 32 nm process for manufacturing of the Clarkdale processor die makes them a very interesting solution for overclocking experiments. We hope the new core will be able to please overclocking fans with extended frequency potential, and its 45 nm addition represented by the GPU and North Bridge won’t become an obstacle.
We overclocked all three Clarkdale processors: Core i5-661, Core i3-540 and Pentium G6950. The tests were performed in a platform based on ASUS P7P55D Premium mainboard. We used Thermalright MUX-120 cooler (with traditionally bent base plate) for all three. It was topped with Enermax Magma UCMA12 fan (1500 RPM). System stability was tested using LinX 0.6.3 utility.
There is only one way to overclock LGA1156 processors: by raising the BCLK clock generator frequency. It is also true for Clarkdale, which is overclocked the same way as Lynnfield processors. Note that the presence of an integrated graphics core doesn’t make overclocking any harder, because it is clocked independently. However, the memory frequency increases proportionally to BCLK clock that is why during overclocking you have to keep an eye on it and correct the corresponding multiplier if necessary.
We didn’t intend to squeeze all the juices out of our CPUs during these overclocking experiments. Therefore, we didn’t increase the CPU Vcore by more than 0.15 V above the nominal. Turbo Boost technology was disabled when we increased BCLK clock.
As a result, Core i5-661 processor with the default frequency of 3.33 GHz and 1.16875 V nominal core voltage overclocked to 4.4 GHz.
With Vcore increased to 1.328 V the CPU passed our stability tests OK. Its maximum temperature during these tests didn’t exceed 72 °C according to the integrated on-die thermal diodes.
The second Clarkdale Core i3-540 has the official nominal frequency of 3.06 GHz. Our sample had nominal core voltage of 1.18125 V.
It overclocked a little worse. This CPU remained stable at 4.25 GHz maximum. In this case its Vcore equaled 31.344 V. The thermal readings during these stability tests again turned out OK: the CPU didn’t heat up more than 72 °C.
Pentium G6950 processor is the hardest one to overclock. Its nominal clock speed is 2.8 GHz, which means that we will have to push BCLK frequency very high up to hit 4.0 GHz or higher, and not all the mainboards can actually allow it. However, it didn’t prevent us from achieving very promising results during our overclocking experiments.
When we increased the core voltage of the test Pentium G6950 processor to 1.328 V, we managed to get it to work stably at 4.4 GHz frequency. BCLK in this case reached 210 MHz, but we didn’t experience any issues after raising the voltage of the North bridge part integrated into the processor from 1.1 V to 1.3 V. I have to say that the absence of Hyper-Threading support in Pentium G6950 has a positive effect on its thermal mode. During overclocking it didn’t heat up more than 66°C, according to the built-in thermal diode.
As we have expected, 32 nm technology used for Clarkdale manufacturing allows overclocking these processors better than Lynnfield. However, 45 nm dual-core Wolfdale CPUs on Core microarchitecture can sometimes overclock even higher with similar cooling. However, those overclockers who search for higher performance should go for Clarkdale, because these processors on Nehalem/Westmere microarchitecture can boast higher performance and will eventually be a faster choice.