Intel Core i7-3960X (Sandy Bridge-E) And X79 Platform Preview

Overclocking Sandy Bridge-E

There is a silver lining, though. Sandy Bridge-E is expected to be overclockable in ways Sandy Bridge is not.

Two of the three SKUs purportedly planned for launch will be multiplier-unlocked, simplifying overclocking quite a bit. Both of those models should support ratios as high as 57x (just like the Sandy Bridge-based K-series SKUs were), easily taking care of the air-cooling community. The third, Core i7-3820, will get a number of accessible bins on top of the highest Turbo Boost multiplier, similar to Core i5-2500 and Core i7-2600.

But whereas P67 and Z68 employed internal clock generators, X79’s BCLK comes from a CK505 embedded clock fed through a buffer (a chip that follows Intel’s DB1200GS Differential Buffer Specification) responsible for “gearing” the frequency.

With Sandy Bridge, if you didn’t have an unlocked K-series SKU, or a partially unlocked Core i5/i7, then you were pretty much stuck. Changing the BCLK frequency directly affected other buses, quickly affecting stability. We’ve been able to push single-digit increases, but anything more than 9 or 10 MHz is asking for trouble. Of course, Intel's intention there wasn't nefarious. By integrating the clock, it cut power use and cost on the 25 and 14 MHz crystals. Inflexible scaling just turned out to be a side-effect.

Sandy Bridge-E should alleviate this somewhat by using the buffer chip to apply one of three different ratios to the BCLK. These will modify the PCI Express bus and DMI, creating a greater range of viable frequency settings. I emphasize the word should because I wasn’t able to get the mechanism working on our lab system. Increasing the BCLK and dropping our -3960X’s multiplier simply kept the platform from POSTing, no matter what combination of settings I used.

At least at first, the question to answer is going to be: who cares, anyway? When you consider the Core i7-2600K is completely multiplier-unlocked, who is going to want to fight a partially-unlocked quad-core -3820 on an expensive new X79-based motherboard? The extra 2 MB of L3 cache, two additional memory channels, and PCI Express-rich processor probably won’t inspire many upgrades. The real candidates for greatness are the six-core models, both of which Intel thankfully leaves unlocked. Specifically, I’m excited to see what the Core i7-3930K can do.

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11 comments
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  • AdrianPerry
    It's a shame Deus Ex: Human Revolution wasn't included in the benchmark testing since we know CPU plays a very big role in the FPS the game can deliver. Other than that, interesting article :)
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  • mathew7
    On the "Hardware Setup and Benchmarks" page, please correct the "Active cores" row with the rest of the table. It should be 1/2 active cores have 6 TB bins and 5/6 have 3 TB bins. After all, it's with 1 active core that 3.9GHz is allowed.
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  • CPU666d1
    Bad luck I can't afford to buy any of these Sandy-E chipsets yet. The Benchmarks ain't too bad either.
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  • ps3hacker12
    too bad its likely to cost three to four times what the current sandy bridge setup costs (a 2600K for example...)
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  • icehot
    Hrm, so basically a little bit of improvement, but mostly extra pci-express lanes, and 2 extra cores, along with additional power draw... Think i'll stick to my 2600k until ivybridge comes out and see what that brings.
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  • mathew7
    icehotHrm, so basically a little bit of improvement, but mostly extra pci-express lanes, and 2 extra cores, along with additional power draw... Think i'll stick to my 2600k until ivybridge comes out and see what that brings.


    You forgot about the additional 2 chanels of RAM. Consider 4 identical modules. With LGA1155, the additional 2 modules (3 and 4) offer only additional RAM, but do not affect performance. On LGA2011, the additional 2 modules also increase memory access speed (think about a 4-lane highway vs 2-lane).
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  • icehot
    mathew7You forgot about the additional 2 chanels of RAM. Consider 4 identical modules. With LGA1155, the additional 2 modules (3 and 4) offer only additional RAM, but do not affect performance. On LGA2011, the additional 2 modules also increase memory access speed (think about a 4-lane highway vs 2-lane).


    That's cool, except I have 2 sticks of 4gb's, I still can't see a need to go beyond 8gb (at home at least). Despite this though, looking at the benchmarks is incredibly disappointing, clock for clock it's generally the same as the 2600k, the only improvement is if something requires 6 cores... For gaming, we all know the additional pci express lanes even in crossfire makes very little difference, maybe a bit more in quadfire, but still, not sure if it's worth it
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  • Gonemad
    I am more concerned if I should start my milling machine for a new copper brick matching the new socket and lineup. We are back at 130W TDP guys. The last generation on that TDP was less than forgiving on air cooling. Or, should it be no concern? Still, that i7-2600k is still crushing the bang-per-buck charts. The new chip should be smashing the previous ones with over 20% difference; instead they are trading punches here and there.
    From my POV, the 2600k is still the best upgrade right now.
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  • bobwya
    mathew7You forgot about the additional 2 chanels of RAM. Consider 4 identical modules. With LGA1155, the additional 2 modules (3 and 4) offer only additional RAM, but do not affect performance. On LGA2011, the additional 2 modules also increase memory access speed (think about a 4-lane highway vs 2-lane).


    Hey dude,

    Hate to break it to you but if you don't need all that memory bandwidth then it's like buying a Ferrari to pootle about town - at 30mph.

    Don't forget that for regular Desktop CPU stuff (web browsing, gaming, etc.) it's memory latency that counts - not bandwidth...

    CPU Architecture #101
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  • Anonymous
    Large amounts of RAM is great for HD Video editing and even more so for the big sample libraries people who make music on their PC use (eg. NI Kontakt, Vienna Symphonic Library, Synthogy Ivory).

    It would be great if all future CPU benchmarks included the DAWbench benchmark. Especially those that feature products not targeted at gamers but at creative people.
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  • mathew7
    Anonymous said:
    Hey dude,

    Hate to break it to you but if you don't need all that memory bandwidth then it's like buying a Ferrari to pootle about town - at 30mph.

    Don't forget that for regular Desktop CPU stuff (web browsing, gaming, etc.) it's memory latency that counts - not bandwidth...

    CPU Architecture #101

    Except that the examples you gave, even memory latency does not affect it much. It's hidden pretty good behing cache.
    But turn to compiling a big project on an SSD(like Android 4 which they say requires 16GB or RAM), and the additional 2 channels give a nice boost. Also video compression scales good with bandwidth.


    And those that have the money and go for "Extreme", those would drive a Ferrary in town at 30mph (ok, maybe 60 if traffic is light).
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