Conclusion

Default

First of all we’re going to have a closer look at performance differences with standard clock speeds. From our overall performance rating we see that the Core i7-6900K is on average 7.96 % quicker than the Core i7-5960X. If we start searching for the benchmarks with best possible scaling on the i7-6900K, then we find that WinRAR runs 16.11% faster on this CPU and Frybench benefits by 15.04%.
We also had a closer look at power consumption and in idle we notice that our test setup with Core i7-6900K was burning 9.37% less power than the same system equipped with Core i7-5960X. In case of load power consumption the difference the new Core i7-6900 is simply in another league, being 29.15% more efficient.

4.2 GHz

Overclocking the Core i7-6900K increases the average performance by 10.76%, while the i7-5960X benefits by 18.50%.
A closer look at power consumption reveals that overclocking these CPUs make for quite a difference. With the Core i7-6900K we see system power consumption rise by no less than 61.23% in idle and 38.18% under load, when comparing with the default power consumption values. In the case of the Core i7-5960X system power consumption goes up by 60.00% in idle and 16% under full load. This clearly shows that from an efficiency point of view, overclocking these processors is not attractive.

4.2 GHz DDR4-3000

Having arrived at this point we’re not going to go through every single benchmark anymore since the overall results are still very similar. What’s much more interesting now is checking what performance differences there are when running DDR4 memory at 3000MHz with both processors, while the stock clocks are DDR4-2133 for the i7-5960X and DDR-2400 in the case of the i7-6900K.
Overclocking the system with the Core i7-6900K inside we notice that the performance goes up by 2.63%. In the case of the Core i7-5960X the difference is 2.82% on average.
Looking at idle power consumption, the system with Intel Core i7-6900K turns 16.50% more energy into heat, whereas with the i7-5960X consumption goes up by 11.51%. Under full load the differences are 4.09% in the case of the i7-5960X and 11.61% for the i7-6900K.

Recommendation

When it comes to price, core and thread count then the Core i7-6900K could be the i7-5960X's direct successor. Both CPUs feature about the same price tag and the both come with 8 cores and 16 threads. Should you be thinking about moving from your i7-5960X to an i7-6900K then you'd be experiencing 7.96% higher performance at stock clocks on average. In order to justify an upgrade you'd have to be able to sell your i7-5960X 7.96% below it's buying price, which is rather unlikely.

Apart from all this you might have noticed that we've conducted our overclocking testing at 4.2 GHz. Initially we wanted to compare the two CPUs at 4.5GHz. While our i7-5960X is well capable of this frequency the i7-6900K wasn't, meaning that the overclocking potential of the new flagship is highly limited. We were also surprised to see that power consumption almost "exploded" when overclocking the i7-6900K, while the i7-5960X is more gentle. If we were to guess, we'd say that there is increased leakage power with the 14nm transistors.
Especially to users overclocking their i7-5960X to 4.5 GHz or higher we can say that their CPU is still very, very fast and there is no need for an upgrade these days.

Page 1 - Introduction	Page 8 - WinRAR / 7-Zip
Page 2 - PCMark	Page 9 - Frybench
Page 3 - 3DMark	Page 10 - HandBrake
Page 4 - XTU	Page 11 - Photoshop
Page 5 - Cinebench	Page 12 - Indice de Performance
Page 6 - SiSoft Sandra	Page 13 - Consommation
Page 7 - Blackhole	Page 14 - Conclusion