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AMD: Two CPUs At 4 GHz

Intel Core i7-875K And Core i5-655K Battle Beyond 4 GHz
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Phenom II X6 1090T

Unlocked Phenom IIs are far less novel—AMD has been doing this for years.

No doubt, the excitement over seeing Intel follow suit stems from the company’s advanced manufacturing technology, which facilitates the massive scalability we got out of the Core i5-655K.

AMD’s 45 nm process is no slouch, though. The company was able to introduce a six-core processor at the same 125W TDP as previous quad-core models. According to AMD, this is a result of adding low-k dielectric material in the metal layers to reduce capacitance. Low-leakage parts mean less heat—and that’s good for overclocking on air (the high-end guys actually prefer high-leakage parts, since they overclock more aggressively, and dissipating heat using LN2 isn’t really a challenge).

I struggled to get the hexa-core 1090T stable at 4.3 GHz with Turbo CORE enabled. Then it was 4.2 or even 4.1 GHz. At each setting, general instability kept us from finishing testing (and heat wasn’t even the issue, despite voltages of up to 1.525V). At the end of the day, the X6 1090T was dialed in at 4 GHz with a voltage of 1.475V. The screenshot below was snapped before we started scaling back voltage at 4 GHz to minimize power use.

I won't be surprised if this chip doesn't make it to my next processor review, though. It was definitely ridden hard and put away wet.

Phenom II X4 965

Available under $200, the quad-core Phenom II X4 965 makes a good contender for the Core i5-655K (though it’s worth noting you can get a six-core Phenom II X6 1055T for less, as well; we simply haven’t purchased any yet).

Our 125W sample proved just as stubborn above 4 GHz as the Phenom II X6 1090T, despite our oversized cooler, 1.5V+ CPU VID, and 1.25V NB VID. Prime95 simply wouldn’t let this chip dig in at 4.2 or 4.1 GHz. Nevertheless, we were happy to settle down to a 1.4625V setting while retaining stability at 4 GHz.  

And with that, all four of our test subjects were running at 4 GHz or higher and ready for a dash through the gauntlet.

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