Intel Core i7-3820 Sandy Bridge-E CPU Review

Author: MAC
Date: February 22, 2012
Product Name: i7-3820
Part Number: BX80619i73820
Warranty: 3 Years
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Sandy Bridge-E: Intel Core i7-3820

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

As you should know by now, Sandy Bridge-E’s naming scheme is greatly simplified when compared to other processor families. While 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. It’s 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 don’t all have the same core/thread count though.

As we stated in the intro, 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. As illustrated above, the Core i7-3820 is a 32nm quad-core/eight-thread processor with a 3.6GHz default clock and a Turbo Boost mode that tops out at 3.9GHz in single and dual-threaded workloads. This default clock speed advantage over its higher-end siblings is a little bit deceptive though, since during our time with the i7-3960X we never saw it dip below 3.6GHz, as long as Turbo Boost was enabled. Accompanying its four cores is 10MB of L3 cache, an impressive 2.5MB per core, and new beefed up memory controller that features a quad-channel DDR3-1600 interface which is theoretically capable of 51.2GB/s of bandwidth.

Core count aside, one of the main differences is that this model is only partially unlocked. What this means is that there are supposed to be 6 bins available above the highest Turbo Boost mode, which would mean that the CPU multiplier is capped at 45X. However, during our time with the processor, and on two different motherboards, 43X was the highest selectable mulitplier. While this might sound terrible, it is not really a big deal and here’s why: 43 X 100MHz (the stock base clock) x 1.25 (gear ratio) equals almost 5.4GHz. In all likelyhood, this multiplier cap is not going to affect anyone’s overclocking fun...unless they are dabbling with sub-zero cooling or yields improve substantially.

On a side note, the Core i7-3820 is actually based on a native quad-core die. Intel's modular die design allows it to easily add or substract parts, so it is quite easy for them to manufacture a seperate die instead of simply using six-core rejects. The fact that the i7-3820 is based on the different M1 stepping instead of C1 or C2 like the higher-end models also lends some credence to this assertion.

Click on image to enlarge

Although our i7-3820 is obviously an engineering sample, it is fundamentally the same as any retail boxed chip that you can buy at your favourite e-tailer, except for what's laser-etched onto the integrated heatspreader.
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 heatspreader, we can determine that this sample was manufactured in the 39th week of 2011, which is just four weeks later than our i7-3960X sample. 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 in there. This is further proof that Intel really geared the LGA2011 platform towards overclockers.

Click on image to enlarge

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 3.6-3.7-3.8GHz depending on the workload. It would very sparingly hit 3.9GHz even in single or dual-threaded workloads, and it was not just a bios issue since we experienced the same situation on two different motherboards. We are happy to report that the new version of CPU-Z finally supports Sandy Bridge-E, and as you can see in the screenshots the core voltage ranged from 0.864V to 1.260V, which is a bit lower than what we saw with our i7-3960X.

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