Broadwell-E: Intel Core i7-6950X, 6900K, 6850K & 6800K Review

Intel Core i7-6800K: Overclocking, Power & Temperatures

Base Clock Frequency, Turbo Boost & Overclocking

Intel's Core i7-6800K is its entry-level Broadwell-E model. Its base clock rate is 3.4GHz and Turbo Boost 2.0 is supposed to max out at 3.6GHz in lightly-threaded applications.

After measuring the processor's stock performance using a taxing gaming loop and full stress test, we worked to determine its highest stable overclock. Unfortunately, we hit a wall quickly, despite some extremely high voltages.

The CPU finished our stress test at 4.5GHz, but despite an extremely high 1.5V Vcore setting, that clock rate proved too aggressive for our gaming benchmark. Dropping to 4.4GHz proved helped stabilize the platform for hours at a time.

Let’s take a look at each core's frequency for the three configurations we tested:

Core Voltage Necessary for a Stable Overclock

In the end, whatever voltage is set in the BIOS only serves as a target that gets adjusted by the firmware depending on load and sensor readings. Let’s take a look at the core voltage that gave us our stable overclock.

Resulting Power Consumption

The following two graphs illustrate average power consumption during idle, gaming and stress testing. The 61W gaming measurement gives you an idea of what overclocking might look like if you want to squeeze every last bit of performance from this processor.

So what happens when the Core i7-6800K is taken to its limits? It might have stayed under the 100W mark at stock clock rates, but the CPU hits a massive 177W at 4.4GHz. The core voltage required to achieve that number is equally gargantuan.

Temperatures During Continuous Operation

So, between the massive waste heat and our high-end cooling, what do the temperatures look like? We averaged all of the cores together as reported by the sensors for each measurement interval and split them into our various workloads.

The results fluctuate according to the gaming load's variable demands. During the stress test, however, temperatures become a lot more consistent, resulting in a smooth curve.

By measuring the temperature of our water, we can see that a good open-loop solution shouldn't have any trouble keeping the Core i7-6800K cool. The CPU will destabilize long before thermal throttling becomes an issue.

Bottom Line

Intel's Core i7-6800K is fairly efficient at its stock clock rates. At 4.0GHz, though, both power use and waste heat increase significantly. While it's possible to push this chip all the way to 4.4GHz, the resulting performance gains just aren’t worth the insane consumption at that speed.

Air cooling is really only an option if you run the -6800K at its stock frequencies. A simple closed-loop liquid cooler is needed to step up to 4.0GHz. At 4.4GHz, there’s no way around a true open-loop setup. For example, a Corsair H100i that we tried was overwhelmed after just 12 minutes, after which the processor throttled due to core temperatures in excess of 90 degrees Celsius.

The amount of waste heat generated by an overclocked Core i7-5960X is manageable. But for Broadwell-E, better heat management is a must.

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  • jt AJ
    was expecting a bit more info and review usage of turbo 3.0. also looks like most of broadwell E chip is junk.. except that one 6850k chip you received probably lucky 1.25v for 4.4v would be good thats only because its broadwell. got one here for 4.8ghz at just 1.22v.
  • Nuckles_56
    Chris, how likely is it that a noctua NH-D15 would be able to cool these heat producing monsters if your h100i struggled and failed with the i7-6800k @4.4GHz.

    But a truly excellent review, even if it does show that there is little reason to go to broadwell-E over Haswell-E
  • elho_cid
    I'd love to step up to the realm of higher core count, but given the results of Adobe SW when scaling to many threads, meas it is not really useful right now. :/
    That's a pity, because the most time I spend staring at a progress bar is when I'm using Adobe products. I don't really need more power to "background tasks" like zipping or lame encoding.
  • AdmiralDonut
    Standard SLI is not limited on the new NVIDIA cards. The only thing that's limited is the new High Bandwidth SLI. Normal 3 and 4-way SLI can be enabled easily by simply asking NVIDIA for an unlock code, something any half way serious enthusiast will most certainly do. Here's some more info on this matter:

    https://www.youtube.com/watch?v=2wBDt9tN5-c
  • bit_user
    I don't really see the point of having a $1700 non-Xeon SKU. Of the few people who can afford it, even less would bother/dare to overclock it.

    I'm still wishing for the rumored 5 GHz SKU to surface. I've rarely needed more than 4 cores, but a couple extra GHz always comes in handy. Even so, I'll not be upgrading until at least Skylake-E or perhaps Kaby-E.
  • Cerunnir
    Quote:
    Chris, how likely is it that a noctua NH-D15 would be able to cool these heat producing monsters if your h100i struggled and failed with the i7-6800k @4.4GHz. But a truly excellent review, even if it does show that there is little reason to go to broadwell-E over Haswell-E


    NH-D15 is arguably better or atleast equal to the H100i when it comes to cooling, and its noise levels is definatly lower both in load and while idle.

    http://www.relaxedtech.com/reviews/noctua/nh-d15-versus-closed-loop-liquid-coolers/2
  • arabesc
    Does it have support for ECC ram?
  • bit_user
    2258219 said:
    Does it have support for ECC ram?
    No. Buy a Xeon version, for that. It's practically the only difference. It's artificial product differentiation, known as "market segmentation".

    Here, you can find links to the specs of the CPUs mentioned in this article: http://ark.intel.com/products/family/79318/Intel-High-End-Desktop-Processors#@Desktop If you view their individual specs, you can see that none support ECC.

    Intel hasn't yet announced the E5-16xx v4 series CPUs, but you can turn up leaked specs with a bit of searching.

    And you'll need motherboard support, too.
  • cats_Paw
    Good review (excellent if its only the heads up for a more in-depth one).
    I have to say that I would love to have a 6 or even 8 core CPU but these prices and performances dont add up.

    In my country a 6700K and a 5820K are priced almost the same, but its still a hard choice (Do i want a "maybe" future proof 6 core that can be good for some work or a 4 core that is flat out faster and cheaper to build around for gaming?).
  • pyoverdin
    Am I correct in saying I could build a PC that's 5 FPS off the 6950X for it's price?
  • chaosmassive
    By Intel pushing out those super chip that I confused of Core, Lane, Cache, etc, etc
    can this "standard" of super CPU cores pushed all other i5 to 150 range and i3 150-100 ?
  • Samer1970
    Chris ,

    Can you please test the 8 cores i7 with HT turned off and compare it to the i7 4 cores at the same clock speed ?

    some games today use 8 threads , and the i7 6700k has 8 Virtual cores while the 6900k has 8 cores and if you turn HT off it will use full speed 8 threads ..

    compare it please ! and compare the Haswell-E 8 cores as well with HT turned off .

    compare i7 4 cores @ 4.4ghz HT (8 virtual cores) VS i7 8 cores @4.4 Ghz NO HT (8 true cores)
  • Samer1970
    AMD ZEN will win this round ... I was expecting the 10 Cores extreme to replace the old 8 cores one .. and that we have $450 28 lanes 8 cores ... but intel chosen to be greedy and ask $1700 instead of $1000 ...

    we need AMD to teach Intel a LESSON.
  • Yuka
    Thanks for the review!

    I would like to see the i7-6850K using a simpler cooling solution (CM 212X, maybe?) and pushing 2x970s or something that a regular non-rich gamer would try and get.

    It's hard to picture these CPUs as gaming power houses, but I do like the MOAR cores approach. F1 and Ashes show what the near future holds, so there's that.

    Cheers!
  • InvalidError
    73949 said:
    It's hard to picture these CPUs as gaming power houses, but I do like the MOAR cores approach. F1 and Ashes show what the near future holds, so there's that.

    Near future? I think we're 10+ years away from seeing the average game being capable of making meaningful use of that many cores. In the near-future, that figure is going to remain under 1% of new games.

    Even among games that do show scaling with extra cores, I'd be curious to see how much time the threads are burning busy-waiting on sync objects - this still counts as CPU usage in Task Manager but produces no useful work.
  • asd_1_
    Just look at ARM efficiency, Intel doesn't have a chance.
  • InvalidError
    2258283 said:
    Just look at ARM efficiency, Intel doesn't have a chance.

    The fastest ARM-based CPUs in mobile devices today are slower than the slowest current desktop i3 despite the i3 having one quarter as many cores.

    The reason why ARM is "so efficient" is because ARM-based CPUs still lack or massively scale down many power-hungry performance tweaks common in desktop CPUs. Until someone puts together an ARM CPU architecture with all those higher power optimizations, ARM will not become a credible threat to desktop CPUs.
  • ajpaolello
    Quote:
    AMD ZEN will win this round ... I was expecting the 10 Cores extreme to replace the old 8 cores one .. and that we have $450 28 lanes 6 cores ... but intel chosen to be greedy and ask $1700 instead of $1000 ... we need AMD to teach Intel a LESSON.


    Sorry I laughed a bit there. AMD can't touch up here although they can try. Plus the more you hype Zen up the bigger the disappointment will be.
  • Sasha dal Ponte
    So, 6700K is still better option for Adobe. Great to know :)
  • Yuka
    125865 said:
    Near future? I think we're 10+ years away from seeing the average game being capable of making meaningful use of that many cores. In the near-future, that figure is going to remain under 1% of new games. Even among games that do show scaling with extra cores, I'd be curious to see how much time the threads are burning busy-waiting on sync objects - this still counts as CPU usage in Task Manager but produces no useful work.


    Nah, not 10+ years away. Take a look at how new game titles are actually expanding on functionality that will require more processing power. I do agree it's hard to have a substantial argument about this, but my take on how the development of games will move forward is through VR and procedural generated content.

    Also, from the general programming perspective, the "busy/wait" issue arises when you're talking about single algorithms made parallel running, but when you're talking about thousands of threads, that is another topic. Context switches become way more expensive than the most hardcore "busy/wait" a single thread can incur into. Then you have, to your point, frameworks still being made more parallel.

    I don't want to go on a big tangent here, but that "it can't scale well beyond 8 threads" is contextualized on an old paradigm.

    Cheers!
  • $1700 for Core 10, Intel must be insane. I was hoping that 10 Core is going to be ~$1000 and 8 core finally become a bit affordable ~$600 but i guess Intel <mod edit> have to come up with a money to cover the failure with mobile chip. Well, <mod edit> you Intel i will stick with i7 3930k (6 Core).
  • dgingeri
    That sounds like my old 4930k, which is currently in my VM server, is better than these new chips. It can overclock to 4.6 at only 1.3V, and can reach 4.7 at 1.4V. What is the point of these new chips if they can't even clock as high as the older chips? This is pitiful.
  • elbert
    Broadwell-E has a major disadvantage in per core performance. Its game performance is well below the Skylake's 6700k. Guess this is why the game list was so lacking. The fact is Broadwell-E only gets a very small advantage over 5820k. The old 5930K is a much better deal than the 6850X due to PCI lane advantage. Mostly the prices are way to high. I suggest Intel drop prices to compete again the 5820k(6800X,6850X), and 5930K(6900X), and 5960X(6950X).
  • dgingeri
    Intel needs to do these things to resuscitate the PC market:
    1. Have more than 5% ipc improvement per generation, or be able to dial up the clocks better
    2. Put more PCIe I/O on the CPUs. The desktop chips should have 32 lanes, minimum, while the HEDT chips should have 64. This limitation of 16 on mainstream chips is BS, and putting more on the chipset is NOT going to make up for it.
    3. Lower prices. They are keeping the prices up and giving us nothing new except maybe using a little less power. What's the point to that?

    Very few people are willing to spend $1000 on a 10% increase in speed or a single feature addition. Intel is specifically the reason why the PC market has become stale. They've dug their own grave. These recent market tactics, especially with AMD lost in the background, are killing all reasons to upgrade PCs from one generation to the next.