Intel Core i7-3960X Sandy Bridge-E Extreme Processor review

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Say hello to Sandy Bridge-E. That’s E for Extreme

Intel’s new Core i7-3960X Extreme processor marks the debut of Sandy Bridge-E. The E suffix stands for Extreme so it follows quite logically that Sandy Bridge-E combines Sandy Bridge Core i5/i7 technology with the sort of thinking that gave us the original Core i7 920 and 965 Extreme.

It’s worth remembering that Intel launched its LGA1366 Bloomfield Core i7 920, 940 and 965 processors in November 2008 and that’s a long time for a processor to claim to be king of the heap. In that three year period we have seen the coming and going of LGA1156 Lynnfield Core i5/i7 and the update of LGA1366 Core i7 from Bloomfield to 32nm Gulftown.

That change boosted the number of cores from four to six in models named Core i7 980 and 990X. The 2011 introduction of the 32nm LGA1155 Sandy Bridge Core i3/i5/i7 pretty much put the tin hat on LGA1366 as it combined superb performance with minimal power draw.

Moreover its sophisticated use of Turbo Boost allowed some models of Sandy Bridge to run beyond their nominal clock speed while unlocked K series models can usually be pushed to 4.5GHz without requiring any extra voltage. The range of Sandy Bridge models starts with dual core Core i3 and runs all the way up to the 3.5GHz Core i7 with four cores and Hyper Threading.

So what’s new?

Sandy Bridge-E adds a dollop of icing to that particular cake and in essence the Core i7-3960X is a Core i7-2700K on steroids. For starters it has six physical processor cores with Hyper Threading which means it can handle 12 simultaneous threads of software.

In addition it has a massive 15MB of L3 cache, supplies 40 lanes of PCI Express bandwidth for multiple graphics cards and introduces a new quad-channel DDR3-1600MHz memory controller. Quad-channel DDR3 means that Sandy Bridge-E motherboards will have either four or eight DDR3 memory slots arranged on either side of the processor socket.

These massive numbers require a huge increase in the transistor count from 1.17 billion transistors in Core i7-980X to 2.27 billion transistors in Core i7-3960X Extreme. Both of those processors use 32nm fabrication technology so the die area for Sandy Bridge-E has increased from 248mm2 to 435mm2 in area.

This enormous processor requires a suitably enormous processor socket so let’s say hello to LGA2011 which is so large that it has two locking levers, one on either side of the CPU. Core i7-3960X has a base speed of 3.3GHz and can Turbo up to 3.6GHz or 3.9GHz, depending on how many cores are working hard. You’ll pay £799 for the privilege of owning Intel’s new champion, so might prefer to save £300 and instead opt for the Core i7-3930K which is 100MHz slower and ‘only’ has 12MB of L3 cache.

Your reviewer has a suspicion that the Core i7-3820 has the greatest potential to deliver a value proposition, if that’s not a contradiction in terms. This model has four cores with HT and 10MB of L3 cache and a higher base speed of 3.6GHz with Turbo however it is locked and does not have the overclocking potential of the 3930K and 3960X which will easily hit 4.5GHz.

The reason we like the Core i7-3820 is that it looks very similar to the Sandy Bridge Core i7-2700K but has the addition of the quad-channel DDR3 memory controller and is expected to sell for about £250.

Motherboards and cooling

Sandy Bridge Extreme is allied to Intel’s new X79 Express chipset which doesn’t seem to bring a great deal to the party as most of the functions are in the processor core. We tested the Core i7-3960X processor using an Asus P9X79 Pro (£240) and a 16GB quad-channel G.Skill Ripjaws Z RAM kit (£80) along with an Intel X25-M SSD and 64-bit Windows 7 Professional. Another significant piece of hardware is the Intel branded Asetek RTS2011LC liquid cooler which retails for around £70.

The cooler is held in place on the CPU with screws that attach to the four corners of the CPU frame. This means there is no backing plate that sits behind the motherboard so there is no need to remove the motherboard from the PC case when you are working with the CPU cooler. Our overclocked Core i7-3960X Sandy Bridge Extreme drew 260W at the wall socket during a CPU test yet it was effectively silent which demonstrates that the Asetek cooler does its job very effectively.

Feel the power

Overclocking the Core i7-3960X was a simple matter with the Asus P9X79 Pro. All we had to do was enter the UEFI set-up screen, open AI Overclock Tuner, select Manual and then let OC Tuner change the necessary settings. The result was a CPU running at 34x126MHz=4.3GHz without any need to manually adjust either voltage settings or Turbo limits. At stock speeds the new Sandy Bridge Extreme has an advantage of ten percent over the 980X Gulftown and this gaps widens under overclocked conditions to some 30 percent. In SiSoft Sandra the Core i7-980X scored 20.64GB/second memory bandwidth while the Core i7-3960X achieved a colossal 37.83GB/second which is considerably higher than the change from triple channel to quad channel had led us to expect.

The quad core Sandy Bridge Core i7-2600K overclocks to 4.5GHz and delivers pretty much the same performance as the six core Core i7-980X. So what about AMD? We tested a 3.3GHz Phenom II X6 1100T as well as the new 3.6GHz Bulldozer FX-8150. The older Phenom II X6 would only overclock to 3.6GHz and drew 260W in the process which was something of a disappointment.

By contrast the FX-8150 would easily overclock to 4.5GHz on air cooling and can be pushed to 7GHz if you take extreme measures. The two AMD processors have similar performance unless you overclock at which point Bulldozer pulls ahead however there is a downside as its eight cores consume 490W of power. Despite having more cores and the ability to run at high clock speed we found that Bulldozer compares poorly with Intel Bloomfield, Sandy Bridge and Sandy Bridge Extreme.

Company: Intel


  • Colossal memory bandwidth, huge performance
  • Epic pricing, high power draw


LGA1366 Core i7 reached the end of the road when Intel launched Core i5/i7 Sandy Bridge. While there is no denying that Sandy Bridge Extreme is a superb update it is, to a certain extent, rather pointless. Intel rules the roost in the desktop PC market with Sandy Bridge and we struggle to think of a scenario where Core i7-3960X Extreme is a legitimate upgrade for the man in the street, especially at such a high price.