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I am overclocking my Core i7 (Ivy Bridge 3770K), aiming for a moderate overclock.
Currently I have it easily stable at a pleasant 4.4GHZ - BCLK defaulted at 100.00MHz, with the multiplier set to x44.

While it is currently stable (tested using Prime95 torture test for a few hours), it does generate some more heat than I would optimally like. Nowhere near overheating, but still requiring the fan to run a bit loud.

I read in this article on Overclock.net, and verified with more experienced overclockers, that lowering the PLL voltage in the UEFI should lower the temperature a little bit.

So, how much should I try to lower it? Just keep going iteratively, as long as it is still stable, or stop arbitrarily at 1.500v (as that article indicates)?
How much could I typically expect to lower the temperature? So far it seems I might have lowered it 2-3C, but its hard to tell since that is less than the fluctuations in ambient temperature.
Most importantly, What exactly does the PLL voltage setting even do? I would feel a lot more comfortable managing this setting manually, if I understood its function. I haven't found anywhere a better explanation of it's responsibilities in the system, other than explaining what a PLL is.

(My motherboard is a GA-Z77-D3H, if it matters...)

AviD
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2 Answers2

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As documented here, the VCCPLL should be 1.80V +/- 5% and is specified at a max of 1.5A, which means it draws a maximum power of 2.835W. Since this is such a very low number compared to the >77W (stock, yours is probably higher) that the whole CPU draws, it will not provide significant power usage reductions. Of course you can experiment, but even if you lower it to 1.5V, you have gained a whopping 0.585W advantage, which is probably not worth the instability it may cause. Try sticking to reducing Vcore as much as possible.

Stefan Seidel
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The PLL voltage setting determines the voltage fed to the CPU's phase locked loop section. The phase locked loop section generates the clock signals for different parts of the CPU that are clocked at different frequencies. It generates the main core clock, the video clock (if the CPU has a video controller), the memory controller clock, the bus clocks, and so on.

The PLL is designed to run at a voltage of 1.8V and exceeding 1.98V is dangerous. However, when overclocking, stability seems to be better for many people in the 1.5V to 1.7V range. The only way it would reduce temperature significantly was if it allowed you to drop the core voltage.

David Schwartz
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