Intel Core i7-3960X review

The Intel Core i7-3960X Extreme Edition is the first processor we’ve seen from the new Intel Sandy Bridge Extreme, or Sandy Bridge E, range. It’s a six-core 3.3GHz processor with a fully unlocked multiplier for easy overclocking, and is squarely aimed at power users and enthusiasts.

There will be three processors in total in the Sandy Bridge E range, all of which require a new socket type – LGA2011 – and a new chipset – Intel X79 Express. The specifications are below.

The differences between the top two chips are fairly small – both have six cores with Hyper-Threading (so the processors show up as having 12 cores in Windows) but the cheaper £480 i7-3930K has 12MB of level 3 cache rather than the 15MB on the top-end chip. Like normal Sandy Bridge chips, the E series’ level 3 cache is shared between all the cores, and each core can grab cache from the pool as it needs it.

The i7-3820 chip is a very different beast, with just four cores and 10MB of level 3 cache, but its higher 3.6GHz clock speed should go some way towards compensating for this. In this regard it doesn’t seem much different from the Sandy Bridge-based Intel Core i7-2600K, which has four cores running at 3.4GHz and 8MB of level 3 cache – look out for our full comparison soon.

A major difference between Sandy Bridge and Sandy Bridge E is that the Extreme chips don’t have on-board graphics; anyone spending this much on an enthusiast chip would most certainly have a dedicated graphics card. However, the lack of on-board graphics does mean that you won’t be able to use Intel’s Quick Sync hardware video-encoding technology.

Next page: Benchmark testing

We tested the Intel Core i7-3960X on an Asus P9X79 Pro motherboard. In our benchmarks, the processor managed an overall score of 123, helped by a strong score of 128 in the image editing test and 133 in the multitasking test. Like Sandy Bridge processors, Sandy Bridge E chips can Turbo Boost to run higher than their stock speeds in lightly-threaded applications; the i7-3960X increased its speed from 3.3GHz to 3.9GHz when running the single-threaded image editing benchmark.

The processor’s six cores also helped in the multitasking test, where the image editing and video encoding benchmarks run at the same time as playing a high-definition video. To check the performance of the individual cores, we disabled all but one core then ran our benchmarks again. With only one core active the processor managed 29 overall – exactly the same as when we ran the benchmarks on one core on an Intel Core i5-2500K, showing the Sandy Bridge E to be essentially a Core i5-2500K with two extra cores.

Strong performance in multitasking, but slower than we were expecting in video encoding

We were surprised, however, that the processor only managed 105 in the video encoding test, which is not much better than a £170 quad-core Intel Core i5-2500K, which scores 100. Video encoding has traditionally taken advantage of multiple cores, and the i7-3960X’s six cores should give it an advantage. However, as we found in our AMD FX-8150 Bulldozer review, many applications struggle to take advantage of more than four cores. During the video-encoding test, Windows Task Manager showed that the i7-3960X didn’t go above 40% usage. Even in the multitasking benchmark we only saw 40-50% usage.

When running two sets of the benchmarks at once, the Core i7-3960X begins to shine

To really max out the processor, we ran two sets of our benchmarks at once, then calculated the average of the scores. In this double benchmark, the processor finally hit 100% usage in the multitasking test, and managed a score of 95 overall – far better than the 56 a Core i5-2500K processor managed in the same test and around 30% faster than the AMD FX-8150 chip’s 64. If you need to run multiple intensive tasks side by side, this is the fastest chip we’ve seen yet.

Next page: overclocking and conclusion

As expected, the processor overclocks well. We turned the multiplier up to 48 to give a 4.8GHz clock speed – about the same as the highest speeds we’ve seen on Intel’s Core i5-2500K. The stable overclock was helped by the RTS2011LC water cooler Intel supplied with the chip, which stayed cool and quiet even with our 1.5GHz overclock; we’re still waiting for a price on the cooler. At this speed, we saw 145 overall in our benchmarks, which is the fastest score we’ve ever seen. However, it’s only four points faster than the Palicomp Phoenix i5 Shinobi, which has a Core i5-2500K running at 4.8GHz – again, showing that applications struggle to take advantage of six cores.

There’s no doubt that the Intel Core i7-3960X Extreme Edition is a hugely powerful processor. However, in real-world tasks it has the same problem as AMD’s eight-core FX-8150 Bulldozer processor, with many applications struggling to take advantage of the extra cores. This still doesn’t stop the Core i7-3960X being the fastest processor we’ve ever seen, but, unless you’re running several intensive applications alongside each other, it’s not drastically quicker than the £170 Intel Core i5-2500K, which is £670 cheaper and requires a far less expensive LGA1155 motherboard. The Sandy Bridge Extreme is the ultimate processor, but most people will rarely find situations where they need that much power.