At the time of our Skylake review of both the i7-6700K and the i5-6600K, due to the infancy of the platform and other constraints, we were unable to probe the performance uptake of the processors as they were overclocked. Our overclock testing showed that 4.6 GHz was a reasonable marker for our processors; however fast forward two weeks and that all seems to change as updates are released. With a new motherboard and the same liquid cooler, the same processor that performed 4.6 GHz gave 4.8 GHz with relative ease. In this mini-test, we tested our short-form CPU workload as well as integrated and discrete graphics at several frequencies to see where the real gains are.

In the Skylake review we stated that 4.6 GHz still represents a good target for overclockers to aim for, with 4.8 GHz being indicative of a better sample. Both ASUS and MSI have also stated similar prospects in their press guides that accompany our samples, although as with any launch there is some prospect that goes along with the evolution of understanding the platform over time.

In this mini-test (performed initially in haste pre-IDF, then extra testing after analysing the IGP data), I called on a pair of motherboards - ASUS's Z170-A and ASRock's Z170 Extreme7+ - to provide a four point scale in our benchmarks. Starting with the 4.2 GHz frequency of the i7-6700K processor, we tested this alongside every 200 MHz jump up to 4.8 GHz in both our shortened CPU testing suite as well as iGPU and GTX 980 gaming. Enough of the babble – time for fewer words and more results!

We actually got the CPU to 4.9 GHz, as shown on the right, but it was pretty unstable for even basic tasks.
(Voltage is read incorrectly on the right.)

OK, a few more words before results – all of these numbers can be found in our overclocking database Bench alongside the stock results and can be compared to other processors.

Test Setup

Test Setup
Processor Intel Core i7-6700K (ES, Retail Stepping), 91W, $350
4 Cores, 8 Threads, 4.0 GHz (4.2 GHz Turbo)
Motherboards ASUS Z170-A
ASRock Z170 Extreme7+
Cooling Cooler Master Nepton 140XL
Power Supply OCZ 1250W Gold ZX Series
Corsair AX1200i Platinum PSU
Memory Corsair DDR4-2133 C15 2x8 GB 1.2V or
G.Skill Ripjaws 4 DDR4-2133 C15 2x8 GB 1.2V
Memory Settings JEDEC @ 2133
Video Cards ASUS GTX 980 Strix 4GB
ASUS R7 240 2GB
Hard Drive Crucial MX200 1TB
Optical Drive LG GH22NS50
Case Open Test Bed
Operating System Windows 7 64-bit SP1

The dynamics of CPU Turbo modes, both Intel and AMD, can cause concern during environments with a variable threaded workload. There is also an added issue of the motherboard remaining consistent, depending on how the motherboard manufacturer wants to add in their own boosting technologies over the ones that Intel would prefer they used. In order to remain consistent, we implement an OS-level unique high performance mode on all the CPUs we test which should override any motherboard manufacturer performance mode.

Many thanks to...

We must thank the following companies for kindly providing hardware for our test bed:

Thank you to AMD for providing us with the R9 290X 4GB GPUs.
Thank you to ASUS for providing us with GTX 980 Strix GPUs and the R7 240 DDR3 GPU.
Thank you to ASRock and ASUS for providing us with some IO testing kit.
Thank you to Cooler Master for providing us with Nepton 140XL CLCs.
Thank you to Corsair for providing us with an AX1200i PSU.
Thank you to Crucial for providing us with MX200 SSDs.
Thank you to G.Skill and Corsair for providing us with memory.
Thank you to MSI for providing us with the GTX 770 Lightning GPUs.
Thank you to OCZ for providing us with PSUs.
Thank you to Rosewill for providing us with PSUs and RK-9100 keyboards.

Frequency Scaling and the Handbrake Problem
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  • StrangerGuy - Sunday, August 30, 2015 - link

    If we keep dropping the OC multi on Skylake we are going into single-digit clock increases territory from 4GHz stock :)

    Yeah, I wonder why AT mentioned in their Skylake review about why people are losing interest in OCing despite Intel's claims of catering to it. From the looks of it, their 14nm process simply isn't tuned for 4GHz+ operation but towards the lower clocked but much more lucrative chips for the server and mobile segment.
  • qasdfdsaq - Wednesday, September 2, 2015 - link

    Then you are deluded. There are edge cases and scenarios that will cause a hardware crash on a Xeon server with ECC RAM at stock speeds, so by your reckoning *nothing* is ever 100% stable.
  • danjw - Friday, August 28, 2015 - link

    When can we expect a platform overview? You reviewed the i7-6700K, but you didn't have much in details about them. You were expecting that from IDF. IDF is over, so is there an ETA?
  • MrBowmore - Friday, August 28, 2015 - link

  • hansmuff - Friday, August 28, 2015 - link

    I assume the POV-Ray score is the "Render averaged PPS"?
    My 2600K @4.4 gets 1497 PPS, so a 35% improvement compared to 6700k @4.4
  • hansmuff - Friday, August 28, 2015 - link

    And of course I mean the 6700k seems to be 35% faster in POV... sigh this needs an edit button
  • looncraz - Saturday, August 29, 2015 - link

    POV-Ray has been seeing outsized performance improvements on Intel.

    From Sandy Bridge to Haswell sees a 20% improvement, when the overall improvement is closer to 13%.

    HandBrake improved even more - a whopping 29% from Sandy Bridge to Haswell.

    And, of course, I'm talking core-for-core, clock-for-clock.

    I suspect much of this improvement is related to the AVX/SIMD improvements.

    Just hope AMD focused on optimizing for the big benchmark programs as well as their server target market with Zen (this is past tense since Zen is being taped out and currently being prototyped.. rumors and some speculation, of course, but probably pretty accurate).
  • zepi - Sunday, August 30, 2015 - link

    One has to remember, that "handbrake" doesn't actually use CPU-resources at all. The process that is actually benchmarked is running x264 codec with certain settings easily accessible by using GUI called handbrake.

    If x264 or x265 programmers create new codepaths inside the codecs that take benefit of new architecture, it received huge performance gains. But what this actually means is that Sandy Bridge and Skylake actually run different benchmarks with different instructions fed to processors.

    Do I care? No, because I just want my videos to be transcoded as quickly as possible, but one should still remember that this kind of real world benchmarks don't necessarily run same workloads on different processors.
  • MrBowmore - Friday, August 28, 2015 - link

    When are you going to publish the runthrough of the architechture?! Waiting impatiently! :)
  • NA1NSXR - Friday, August 28, 2015 - link

    Sigh, still no BCLK comparisons at same clocks. What would really answer some unanswered questions would be comparing 100 x 40 to 200 x 20 for example.

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