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Step 1: Finding The Overclocking Limits

Core i7-870 Overclocking And Fixing Blown P55-Based Boards

One of the top two finishers in our previous motherboard round-up, Asus’ P7P55D was chosen for its stability and ability to support this tester’s legacy drive-imaging software. The top two finishers were close enough in their overclocking capabilities that this one feature was enough to tip the scales, because having an image of the fully-loaded drive is a great way to circumvent hours of reloading should an overclock corrupt the operating system partition.

We’ve been using 1.45V to gauge overclocking capability in every large motherboard roundup since Intel introduced its 45nm manufacturing process in Core 2 Duos. This particular setting has given us fairly consistent results beyond four gigahertz for everything from the lowly Pentium E5200 to the latest LGA 1366 and LGA 1156 Core i7s.

At 1.448V, our Core i7-870 reached 4.28 GHz, a number we rounded up to 4.3 GHz in today’s charts. Focusing on CPU power and performance, we dropped the memory multiplier to 5x BCLK and retained our previous review’s 8-8-8-24 timings.

The highest voltage we’ve seen our processor reach at stock settings is 1.25V, with all the power-saving, voltage-changing features enabled. Of course, those features don’t work well in a maximum overclock attempt, since any voltage dip or multiplier increase can lock the system. Interested to see how far the “stock-max” voltage would take us, we manually configured the BIOS to produce a 1.248V result under full load, with power-saving features and Turbo Boost mode disabled.

While Intel's Turbo Boost mode can take the processor to 3.20 GHz with four cores active, we managed to reach 3.77 GHz without pushing the voltage envelope. The loss of power savings features substantially decreases partial-load efficiency, but this indicates that Intel could, in theory, make a higher-model processor using the same core.

Now that we’ve discussed the maximum and minimum voltage levels we’d choose for overclocking, a third setting will show whether power consumption rests on a curve or a slope. The middle setting of 1.35V coincides with what many builders believe is a perfect balance of good overclocking and years of stable operation.

Overclockers interested in ultimate longevity will be happy to see we reached 4.04 GHz at 1.344V under full load, a number we rounded down to 4.0 GHz for today’s charts.

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