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Is Core i7-3960X An Efficiency Winner?

Sandy Bridge-E: Core i7-3960X Is Fast, But Is It Any More Efficient?
By , Achim Roos

Because we just reviewed Core i7-3960X, most of the performance results in this article don’t come as a surprise. Intel’s latest desktop processor is a beast in that it delivers unmatched performance per clock with the added benefit of six cores. As a result of its architecture and scalable ring bus, the beefed-up Sandy Bridge-E enables an additional two cores on the desktop, and will soon facilitate up to two more on the Xeon E5 family. Although a quarter of its available shared L3 cache is disabled, access to 15 MB represents a substantial increase from Gulftown's 12 MB. And clock rates as high as 3.9 GHz with one or two cores active (by virtue of Turbo Boost) augment performance in less-optimized apps. Otherwise, the technology manages to push a 3.3 GHz base clock up to 3.6 GHz, even when the chip is fully-loaded.

All of this is made possible at lower idle power use compared to last generation's hexa-core flagship. And, armed with a modest Radeon HD 6850, system power use drops as low as 62 W. Even a high-end GeForce GTX 580 doesn't push the machine beyond 90 W. Considering that older systems often incur more than 120+ W of consumption, it's clear that Intel's Sandy Bridge design pushed beyond simply increasing performance.

However, peak system power consumption goes up quite a bit. This is attributable to the large, complex die and the fact that it's pushed hard by technologies like Turbo Boost to maximize performance in every conceivable workload. Because we used a capable closed-loop liquid cooling system, the processor's maximum speeds were maintained for longer intervals than on average air-cooled solutions. We're not looking at an affordable quad-core LGA 1155-based chip here; expensive cooling is the price enthusiasts have to pay for the extra performance.

Sandy Bridge-E is the undisputed performance winner, and, for the first time, I'd label this high-end configuration reasonable with regard to idle power use. However, two additional cores and the extra cache on a very large die impose greater power requirements under load than they add to the performance charts. As a result, Intel's mainstream Sandy Bridge processors end up outshining Sandy Bridge-E in every measure of efficiency. Unless you really need a hexa-core platform for its raw performance (power be damned), existing Core i5 and Core i7 chips able to drop into LGA 1155 are more sensible solutions.

For obvious reasons, efficiency does not scale linearly with core count, necessitating a revised answer to my initial question: Sandy Bridge-E delivers more efficiency than other six-core processors. However, it's hard to make that -E represent efficiency. If that's the metric you're looking to optimize, drop the -E suffix altogether, and save money now (on the hardware) and over time (on power) with Intel's year-old mainstream Sandy Bridge processors.

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