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Now, you don’t swap out a $300 motherboard for a $225 platform and expect the same experience, so I initially tempered my expectations of overclocking on ASRock’s X79 Extreme4-M.
That was premature, though. Using the company’s latest firmware, I had no trouble booting up at 4.4, then 4.5, 4.6, and finally 4.7 GHz. Those last two frequencies were fine for benchmarking, but they gave out under IntelBurnTest, compelling me to settle in at a modest 4.5 GHz.
I could have gone higher. The chip’s power consumption crested at 183 W at 1.375 V, and ASRock indicated to me that its board should take 200 W or so. Given a 91°C ceiling and temperatures that topped out around 80°, thermals weren’t the problem. The Core i7-3930K wanted more voltage. But even the settings I used aren’t guaranteed to be safe over the long term, so it wasn’t worth it to me to nudge up to 1.4 V.
With all of that said, 4.5 GHz was rock-solid down at 1.361 V, so long as the most important variable was controlled: cooling. I used Intel’s RTS2011LC for my processor, which left the X79 Extreme4-M’s VRM vulnerable. Naturally, instability ran rampant even at lower power levels. Simply adding a fan blowing over the motherboard solved all heat-related issues.
As a general rule of thumb, it’s possible to get great clock rates from the Sandy Bridge-E-based chips we’ve tested, so long as you’re willing to put plenty of voltage through them and throw big cooling at the resulting heat. We’ve talked to system builders willing to go 4.4 GHz on shipping machines, so our 4.5 GHz overclock on a retail-purchased processor turns out to be pretty solid.
The Core i7-3820 hits respectable frequencies as easily, but it requires a slightly different approach. Because it’s neither an X- nor a K-series SKU, the -3820 is constrained by “limited overclocking.” In short, it scales up to six 100 MHz bins beyond its maximum Turbo Boost clocks. With three or four cores active, it hits 4.3 GHz. When one or two cores are busy, it jumps to 4.4 GHz.
That leaves performance on the table, though, making it necessary to exploit the strap ratios incorporated into the X79 Express platform. ASRock’s X79 Extreme4-M doesn’t expose them explicitly, though we’ve asked the company to add the ratios, and it now plans to. However, manually specifying 125 MHz, for example, allows the PCI Express and DMI buses to remain within spec.
Interestingly, our -3820 didn’t want to run at 4.5 GHz, but it worked at 4.625 and 4.75 GHz using 37x and 38x multipliers. Still finicky, it wouldn’t complete the entire benchmark suite, even with a longevity-unfriendly 1.44 V driving it. But my expectations for this one weren’t high anyway. And if you need a quad-core chip, I don’t see any reason to buy a high-end platform (X79), quad-channel memory kit, and a locked processor when the Z68/Core i7-2600K combo is cheaper, still very capable, and equipped with Quick Sync support.