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More Voltage, More Heat

Overclocking Core i7-3770K: Learning To Live With Compromise
By , Achim Roos

Our evidence shows that, at similar clock rates, 32 nm Sandy Bridge-based processors don't get as hot as the new 22 nm Ivy Bridge-based chips. As a result, our Core i7-3770K dropped its overclocked frequency sooner in order to protect the CPU's integrity, nullifying the effects of our overclocking efforts entirely. It also discourages setting higher core voltages, since that'd just exacerbate the issue.

Thus, throttling can only be avoided when the target overclock is achieved using the lowest core voltage possible. However, it still has to be high enough to allow the transistors to operate reliably. Old mantras like “a hefty voltage increase helps facilitate a hefty frequency bump” do not work on Ivy Bridge-based chips. Once throttling kicks in, average clock rates drop to around 3.6 GHz. That's a significant reduction compared to the 4.6 GHz we were targeting.

We think that you're going to have the most success overclocking Ivy Bridge if you can stay as close as possible to the CPU's default voltage setting or work really hard to overcome the heat resulting from more aggressive voltage settings. At 4.6 GHz, the voltage increase necessary to get our machine stable quickly resulted in throttling, forcing us to stay at 4.5 GHz. At that speed, we had to increase the core voltage by 70 mV in order for our benchmark suite to run reliably.

As in our launch coverage, 4.5 GHz turned out to be as high as we could go without running into stability issues. It wasn't difficult to get up to 4.7 GHz (or, using one of our samples, even 4.9 GHz). But certain tests consistently cause those frequencies to derail, pushing us back down.

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