Intel Core i7-3960X Review: Sandy Bridge-E And X79 Express

Intel's Sandy Bridge design impressed us nearly a year ago, but it was intended for mainstream customers. The company took its time readying the enthusiast version, Sandy Bridge-E. Now, the LGA 2011-based platform and its accompanying CPUs are ready.

According to Mick Jagger, it’s lonely at the top. Intel might agree. After all, for the past five years, the company has put an increasingly large gap between its fastest desktop processors and AMD’s own best efforts. Enthusiasts tend to lament the fact that a lack of intense competition means they pay more for high-end hardware. But, if you’ve been around long enough, you know that Intel’s Extreme Edition CPUs were always £800 affairs and, once upon a time, AMD’s vaunted FX-series chips used to be worth their £500+ asking prices.

The fact that the £800 price point persists today, eight years later, means Intel recognizes the extremely limited market for these flagship desktop processors and isn’t about to push one of its crown jewels even further out of reach. 

It comes as little surprise, then, to see yet another Extreme Edition processor hovering around this high price point. But this behemoth is very different than what came before.

The prior generation of flagship parts based on Gulftown came armed with six physical cores and up to 12 MB of shared L3 cache. They boasted LGA 1366 compatibility, extending the useful lives of pricey X58 Express motherboards, helping soften the blow of £400+ processor upgrades. No such luck this time; you’re facing a pricier investment.

Sandy Bridge-E, Gulftown’s successor, employs an LGA 2011 interface, requiring new motherboards based on Intel’s X79 Express Platform Controller Hub. It also comes armed with an integrated quad-channel memory controller, necessitating four-module memory kits. Oh, and then there’s the fact that Intel isn’t planning to bundle its new chips with coolers, requiring a separate purchase there, too.

Meet Sandy Bridge-E

Intel is announcing three Sandy Bridge-E-based models today, but only two will be available through the end of 2011: Core i7-3960X and Core i7-3930K. The third, Core i7-3820, is slated for a Q1 2012 introduction.

All three employ the same die, which is composed of 2.27 billion transistors and measures 434 square millimetres (making it a very big chip). In comparison, quad-core Sandy Bridge parts are made up of 995 million transistors and measure 216 square millimetres, while six-core Gulftown CPUs incorporate more than 1.1 billion transistors in a 248 square millimetre die.

Of course, Sandy Bridge-E was never intended to be a desktop processor exclusively. Rather, it’s going to emerge in the first part of next year as Xeon E5 for single- and dual-socket servers/workstations. In that context, the CPU’s size and complexity makes more sense. After all, Westmere-EX (at the heart of Intel’s more enterprise-oriented Xeon E7 family) is a 2.6 billion-transistor die occupying 513 square millimetres of space.

When Sandy Bridge-E surfaces as Xeon, it’ll offer up to eight processing cores and 20 MB of shared L3 cache. As a desktop CPU, however, it’s limited to as many as six cores and up to 15 MB of shared L3. Intel achieves this by disabling two cores and four of the die’s 16 slices of shared L3 cache.

Of course, that configuration only applies to Core i7-3960X. Core i7-3930K, which also features six cores, dips down to 12 MB of cache, revealing Intel’s ability to very granularly disable pieces of the shared L3 to suit its needs. The upcoming Core i7-3820 will employ four cores and 10 MB of shared L3 cache—essentially half of a Sandy Bridge-E die. Each core includes 32 KB of L1 instruction and L1 data cache, plus a dedicated 256 KB L2 cache. 

Sandy Bridge-E Family

Base Clock
Max. Turbo
Cores / Threads
L3 Cache
Core i7-3960X
3.3 GHz
3.9 GHz
6 /12
15 MB
130 W
4-Channel DDR3-1600
Core i7-3930K
3.2 GHz
3.8 GHz
6 / 12
12 MB
130 W
4-Channel DDR3-1600£479.98
Core i7-3820
3.6 GHz
3.9 GHz
4 / 8
10 MB
130 W
4-Channel DDR3-1600TBD

The clocks on all three SKUs range up and down as well. The -3960X starts at 3.3 GHz and, through the same second-gen Turbo Boost technology introduced with Sandy Bridge, speeds up to 3.9 GHz. The -3930K starts at 3.2 GHz and hits a peak of 3.8 GHz in lightly-threaded workloads. Finally, the -3820 will start at 3.6 GHz and reach frequencies of up to 3.9 GHz with Turbo Boost.

Of course, the X- and K-series chips are also multiplier-unlocked, making those stock clocks pretty much meaningless for most enthusiasts planning to tweak their systems. Intel calls the -3820 “partially unlocked.” In all actuality, it gets six 100 MHz bins above its maximum Turbo Boost setting of 3.9 GHz, translating to a ceiling of 45x.

Intel is using the same cores found in its Sandy Bridge-based CPUs. Turning off Turbo Boost, setting similar base clocks, and running a couple of single-threaded apps demonstrates the efficient execution Sandy Bridge brings to the table compared to Thuban or Zambezi.

Switching Turbo Boost back on and running Core i7-3960X in parallelized and single-threaded titles gives us a better impression of what that technology does for performance.

In an application like iTunes, which is only able to utilize one core, Turbo Boost improves performance by 12.8%. In 7-Zip (well-optimized to use available cores), it increases performance by 10.8%. The second number is surprisingly high because Turbo pushes an additional three 100 MHz bins when five or six cores are active and none of the technology’s triggers are tripped. As a result, it's tackling our compression workload at 3.6 GHz instead of 3.3.

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  • flong
    Wow, I am so underwhelmed. My 2600K is looking better and better ha, ha. Yea there is an average performance increase of 17% over my 2600K but this CPU costs $1000 - honestly I don't get the $700 difference other than it MAY support PCI-E 3.0 (we don't know for sure). For those that use Premier Pro and ABBYY Fine Reader and other specific programs like them, then yes there is a real tangible benefit.

    For gamers there is virtually no real benefit worth $700. It is entertainingly funny that SLI performance doesn't change much between the 2600K and the 3960X. The only real benefit to gamers will again be PCIE 3.0 support IF the Sandy Bridge E chips will support this.

    I guess I was expecting more oomph from this new flagship. A measly 17% average performance increase over my $292.00 2600K makes me think that I have the best CPU available for the money. When we see how the new Sandy Bridge E CPUs overclock this may change greatly because there is every indication that they will be amazing overclockers. That coupled with PCI-E 3.0 capability may provide some separation between the Gen 2 and Gen 3 E CPUs.
  • Magic Man
    Is it really that suprising though since they are the same cores? Nobody really expected much more than a marginal increase core for core, the difference in the platform comes with addition of those two extra cores (in the hexcore chips obviously) that are not available in the standard sandybridge package.
    And, don't compare with the top end six core but the 3930 which offers far better value for money for those extra cores, extra cache and the platform advantage of 4 channel memory with a cheap 32GB option or more expensive 64GB option - again, something that is not available to the cheaper sandybridge platform.

    Nobody knows what performance increase Ivybridge will bring, it may be great but will still be limited to four cores in the standard platform, hopefully Ivybridge-E wont take longer than this time next year and will offer at least a six core option if not eight core to the desktop if Intel don't decide to kill the two extra cores as they have done with the desktop sandybridge-e
  • theFatHobbit
    Is the main selling point for this over the gulftown the improved energy efficiency?
  • Anonymous
    The Visual Studio benchmark looks suspicious to me: A 6 core only showing a few percentages improvement vs a quadcore? What is the unit of time of that test, minutes or seconds? Compilation should be perfectly scalable (with the correct tools).
  • techpops
    OK first of all, great article. Really enjoyed reading about the new processors. I was a bit miffed there wasn't a Cinebench score as Cinema4D is what I live in. I'll add those scores here for anyone interested.

    Straight i7-3960X = 10.55
    Overclocked = 12.31

    Anyone into 3D and Cinema in particular will be looking at those figures and drooling. Is it worth the cash considering everything you need to buy if you render at home? not really. You can get close to a 10 score with an overclocked i7-2600k and the massive expense of a 3960 could see you building two or three 2600k boxes to get scores of close to 20 and 30 respectively. Of course that's only going to be meaningful to animation heads using separate machines to render different frames in an animation, but as that's really all they need, more cores, more gigahertz's, Intels latest offerings aren't priced right to attract them.

    Looking at the cheaper chip, it still doesn't really make sense to go for it in a graphics workstation. You will get far more performance and value from just building the cheapest second 2600k box you can. A big shame really as it feels like we are doomed to a certain level of computing in one computer for at least the next two years with small percentage bumps along the way unless you're willing to go way out there on the money tree.

    Intel are a bunch of meanie heads putting the prices of these so far out of reach of us peons.
  • flong
    Take heart, Ivy Bridge is coming out int 2012 and hopefully it will be the real-meal deal. I am somewhat stunned that my 2600K has such staying power. Except for the new PCI-E 3.0, I don't see much reason for upgrading my CPU.

    Still, that being said, when you take a look at the performance increases on some specific programs they can be dramatic - some are as much as 50% faster than the 2600K. There is some real improvement in many areas with the 3960X.
  • techpops
    flongTake heart, Ivy Bridge is coming out int 2012 and hopefully it will be the real-meal deal. I am somewhat stunned that my 2600K has such staying power. Except for the new PCI-E 3.0, I don't see much reason for upgrading my CPU.Still, that being said, when you take a look at the performance increases on some specific programs they can be dramatic - some are as much as 50% faster than the 2600K. There is some real improvement in many areas with the 3960X.

    @flong I agree the top end chip especially is a beast. For the kind of work I do it would be a huge benefit but as I'm only a hobbyist at this, these prices can't be paid for by saying a next big budget job will pay for the new hardware as any real business could.

    Also I think as even the Toms article points out, with the perspective change on the 2600k initially looking a bit of a miss up against the almost as good 2500k. Looking at it today the 2600k clearly shines when placed in line with these new chips. So it's less about the 2600k holding its own and more about Intel refusing to let us all at the good stuff in new hardware, instead concentrating on super high profit margins they can get from business.

    I'm assuming the enthusiast and really anyone falling in the can only afford a 2600k market is quite small compared to where these 3960X's are being targeted so at least until that sector gets chips that are much faster again than the 3960X's, I don't really see Intel giving us anything significantly better for at least the next two years. Whatever launches next year can't really be as fast as a 3960X and priced just above a 2600k or it would invalidate the pricing structure they already have in place. So really how can you expect anything more than a few percent bump?

    With AMD floundering around like sad fishes out of water, Intel just have no reason to really push the value.

    "This news just in" Fire brigade saved the day at a local IT business today, the fire initially started when staff decided to cook their fried breakfasts on the AMD Bulldozer server cases instead of ordering out. Fireman Sam who was at the scene is urging others not to cook on AMD products but suggests heating sandwiches in bulldozer hot swappable drive bays is OK"
  • flong
    I think that Ivy Bridge is supposed be a step up from Sandy Bridge E, but I am really tired right now ha, ha.
  • Idonno
    I really don't why anyone is even the least bit surprised with the small performance increase of Intel's new extreme CPU.

    People everywhere have always paid dearly for that last little bit of performance and it really doesn't matter whether we are talking about tennis rackets, fishing poles or technology!

    The last 10% will always cost exponentially more than the first 90% .