Intel Sandy Bridge-E Core i7-3960X CPU Review

Author: MAC
Date: November 14, 2011
Product Name: i7 3960X
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Sandy Bridge-E: Intel Core i7-3960X Extreme

Sandy Bridge E/Sandy Bridge/Gulftown/Zambezi - Click on image to enlarge

Before we get into the nitty-gritty details, letís first talk about Sandy Bridge-Eís naming scheme. The Sandy Bridge LGA1155 models are part of the Core i3/i5/i7 2000 series, which consists of numerous models with different core counts, threads counts, IGP types, and supported technologies. Itís a bit of a mess. Thankfully, Sandy Bridge-E (SB-E) has been given the 3000 series moniker, and they are all Core i7 models, which simply put means that they all support Hyper-Threading (HT) and Turbo Boost technology. As you will see below, they donít all have the same core/thread count though.

As you can see from the die size, transistor count, and the side-by-side comparison at the top of the page, the SB-E has a really big core. In fact, it is by far the largest core that has ever trickled down to the consumer market, being 25% larger than the 346mm2 Phenom II X6ís Thuban die. It is almost 40% larger than the ďeight-coreĒ Bulldozer die, which itself features 2+ billion transistors. The SB-E is also almost exactly twice as large as the original Sandy Bridge die, which initially makes sense since SB-E is in fact a native eight-core chip. However, SB-E processors donít have an integrated GPU. What is taking up all that extra die size is the huge L3 cache, the double-sized memory controller, and more complex PCI-E controller. None of this impacts or even interests your average consumer though, so letís move on to something more tangible.

The Core i7-3960X Extreme Edition model that we are reviewing today is a six-core/twelve-thread processor with a 3.3GHz default clock and a Turbo Boost mode that tops out at 3.9GHz in single and dual-threaded workloads. While this is not breaking any new ground with regard to frequency, during our time with the chip we never saw it dip below 3.6GHz, and you can honestly consider that the true default clock if you keep Turbo Boost enabled. Since this is an Extreme Edition model it does feature fully unlocked multipliers, so those with more lofty frequency aspirations will be able to satisfy their need for speed. Accompanying these six cores is 15MB of L3 cache, the most of any desktop processor, and new beefed up memory controller that features a quad-channel DDR3-1600 interface which is theoretically capable of 51.2GB/s of bandwidth.

For those who arenít willing to sell a kidney, the i7-3930K is a very attractive proposition. Basically, it is exactly the same as its big brother, just clocked 100MHz lower and with 0.5MB less L3 cache per core. Since it is a K-series model it also features fully unlocked multipliers and has all the same overclocking capabilities as the Extreme Edition model. At $555, it is a very nice replacement for the $580 i7-980 (non-Extreme).

Arguably, the most interesting chip of the series is the Core i7-3820. Intel is clever, and with this model number they are clearly hoping to evoke the undying love that most enthusiasts had and continue to have for the i7-920. Although this model only has four cores, it features the highest default clock frequency of the bunch. Core count aside, one of the main differences is that this model is only partially unlocked. What this means is that there are Ďonlyí 6 bins available above the highest Turbo Boost mode, which is to say the CPU multiplier is capped at 45X. While this might sound terrible, it isnít and hereís why: 45 X 125MHz (a realistic base clock) x 1.25 (gear ratio Ė a new feature) equals 7.0GHz. Clearly, this multiplier cap is not going to affect anyoneís overclocking fun. We donít yet know the price point for the i7-3820, but we can narrow it down to above $300 and below $370. Availability for this particular model will be sometime in Q1 2012.

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Intel didnít provide us with any retail packaging, but here is a render of the boxes. Itís basically the same style that was introduced with the Sandy Bridge LGA1155 series.

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If you thought LGA1366 processors were big, wait until you have one of these in your hand. These new SB-E chips are downright enormous, which is understandable given the fact the package has to fit 2011 contact points.

Based on the digits on the integrated heatspreader (IHS), we can determine that this sample was manufactured in the 34th week of 2011, which is exactly one year older than our i7-2600K media sample. One full year of further improvements to Intelís industry-leading 32nm manufacturing process? We canít wait to see how it overclocks.

By the way, notice that little black dot on the bottom-right corner of the HIS? Intel has drilled holes in all the SB-E chips in order for enthusiasts to place a thermal probe there. How cool is that? And do we need any further proof that Intel has really geared the LGA2011 platform to overclockers? We think not.

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As mentioned above, we never saw the default 3.3Ghz clock speed. At idle, the chip would drop down to 1.2GHz, and under load it would alternate between 3.6-3.7-3.9GHz depending on the workload. On a side note, we donít think CPU-Z currently fully supports either this chip or our Intel-provided motherboard, so we would take the vCore figure with a grain of salt. Using AIDA64, we saw the core voltage range from 1.141V to 1.266V, which is quite reasonable if accurate.

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