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Efficiency: Optimizing The Clock Rate Of AMD's Phenom II X6


The Phenom II X6 means a lot to AMD, being the firm’s top desktop processor at this time. Although it’s not capable of beating the Intel Core i7-980X hexa-core CPU, which is superior in all benchmarks, AMD finally managed to reenter the enthusiast space by providing maximum value at a $300 price point.

Every Intel processor you see at $300 will most likely deliver equivalent or less performance (depending on the workload), and every bit of additional performance you can get in Intel’s Core portfolio will directly and disproportionately impact your spending. Similarly, it’s relevant to note that AMD requires six cores to deliver the performance level Intel enables with only four, but allow me to quote an Intel PR person who defended Intel’s dual-die, quad-core architecture against AMD’s monolithic quad-core die design a few years ago: “Only the results count.”

From this standpoint, AMD is very focussed and delivers excellent value. The processor overclocked nicely, but not amazingly well. We couldn’t reach more than a 3.8 GHz clock speed reliably with our sample, although there have already been reports of somewhat better results. Keep in mind that adding cores makes overclocking harder, expecially if the chip still employs 45 nm manufacturing.

What’s more interesting, though, is power efficiency. Performance per watt isn’t ideal at AMD’s 3.2 GHz stock speed. We found that a slight overclock to 3.4 or 3.6 GHz doesn’t require much voltage increase, nor does it change system idle power. But it does provide a decent performance bump at peak load, which has the processor deliver more overall performance per watt. The side effect is that the six-core Phenom II X6 will then always be faster than the Phenom II X4 965 at 3.4 GHz. Surely, you can't lose there.