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Intel Core i7-3960X Extreme Edition Review
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by Rob Williams on November 28, 2011 in Intel Processors

To those looking to build the biggest, baddest high-end PC around, the wait for Sandy Bridge-E was no doubt painful. But, it’s finally here, and much to our expectations, Intel has once again solidified its position as the performance leader. So let’s take a look at what it offers, and compare it to the i7-990X, i7-2600K and AMD FX-8150.

What Sandy Bridge-E Brings to the Table

As its name suggests, Sandy Bridge-E (‘E’ as in Extreme) isn’t that different from the original Sandy Bridge released this past January. The most notable change actually comes in the form of a removal, with Intel lobbing off its integrated graphics processor (IGP).

It’s hard to fault the company for that decision. Much like the reason for not including a cooler with the CPU, it’s highly unlikely that many people will even notice an IGP gone. Not to mention, the die is big enough as is without it. There is a small caveat, however – Intel’s own QuickSync technology will not be possible on this platform. Whether that will matter to many people, I’m unsure.

Aside from the removal of the Intel HD Graphics processor along with some slight rearranging, little has changed with regards to the die. To accommodate more than four cores, Intel has placed the shared L3 Cache to sit in the middle of the two groups of four cores, while the queue and I/O has been placed on top, and memory controller on bottom.

With the goal of increasing performance by improving efficiency, Intel introduced a ring-style interconnect on the original Sandy Bridge that allowed key CPU components the ability to work better with each other. That remains on Sandy Bridge-E, with the CPU cores, L3 Cache and integrated memory controller (IMC) all getting in on the interconnect action.

Intel Core i7-3960X Die Detail

Sandy Bridge-E is an architecture that’s inherently designed to support 8 cores, 16 threads and 20MB of L3 Cache, but as the die shot above shows, two of these cores are disabled on launch products. If that seems odd, it’s because it kind of is. Could Intel be planning an 8-core variant in 2012? At this point, it’s hard to say.

The company is slated to release server variants of Sandy Bridge-E in early 2012 that feature 8 cores and 20MB of Cache, so yields clearly aren’t the problem here. What is? Two scenarios come to mind. Intel either couldn’t assure total stability at the clock speeds it wants in an enthusiast part on an 8-core offering, or it became a battle of having to adhere to its traditionally strict TDP limit of 130W.

As it is, rumor has it that Intel’s 8-core SB-E server variants will not include the Turbo feature at all, and that the top-end part will sit at 3.0GHz. That’s a far cry from the 3.3GHz base clock for the i7-3960X and its 3.90GHz Turbo. Likewise, the top-end server part that will use Turbo is essentially 1:1 with the i7-3960X.

That all said, it’s impossible to predict Intel’s next move here. While it would be possible to release an eight-core part with scaled-back frequencies, that would automatically make the offering look odd compared to the i7-3960X’s higher clocks. It’s an interesting trade-off.

But, let’s get onto other things, shall we? In addition to its six-core likeness, Gulftown offered something else that Sandy Bridge couldn’t: the ability to use dual graphics cards at x16. Sandy Bridge-E carries that ability over and officially supports up to three GPUs at x16/x16/x8, four GPUs at x16/x8/x8/x8 and five GPUs at x16/x8/x8/x4/x4.

Intel X79 Express Chipset Block Diagram

I don’t want to get too far off track, but prior to Sandy Bridge-E’s launch, NVIDIA shared some information that surprised me. It seems that with the X79 platform as a whole, along with the ability to run three graphics cards at x8 or higher, 3-way SLI will see up to a 30% performance boost on a PC with the Core i7-3960X processor compared to an X58 machine with the Core i7-975 (six-core vs. quad-core, but I don’t think that matters). Interesting stuff. It’s clear that no other platform will be able to accelerate the multitude of console ports in 3-way SLI as X79!

Intel X79 Express Chipset Block Diagram

Back to the chipset. With X58, Intel introduced a triple-channel memory controller, and where bandwidth was concerned, there was just no comparison. Depending on the configuration, we saw a bandwidth boost of about 100% compared to a dual-channel implementation. With X79, Intel bumps the IMC up to a quad-channel, capable of delivering unparalleled memory bandwidth – a theoretical 51.2GB/s when using the maximum officially-supported DDR3-1600 modules.

All of the other chipset features are typical and expected. There are 8x PCIe lanes at 1GB/s each, a total of 14 USB 2.0 ports, integrated NIC, 2 SATA 6Gb/s ports, 4 SATA 3Gb/s ports, and the latest iteration of Intel’s Rapid Storage Technology (3.0).

As always, Intel is releasing a flagship motherboard with this launch. Codenamed “Siler”, the DX79SI aims to be the ultimate enthusiast board. Though the X79 chipset doesn’t support USB 3.0, Intel includes two such ports on here anyway, along with 6 USB 2.0 ports, dual Intel LAN ports, full audio, a CMOS reset button on the back and triple x16 PCIe slots.

Intel DX79SI 'Siler' Motherboard

While not as important as the board itself, Intel has pushed out its coolest box art yet with this one:

Intel DX79SI 'Siler' Motherboard

All of our Core i7-3960X benchmarking was conducted on the DX79SI, although my experience with the board is mixed. There were a couple of niggles that lead me to believe that we’ll be seeing a fair number of EFI updates in the future. Intel remains committed to its motherboard solutions, however, so things should only get better.