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 i7-5930K is on average 3.66 % quicker than the Core i7-5820K. Both processors come with six cores and twelve threads, the difference between the two processors are the default base frequency where the 5930K is 200MHz faster than the 5820K which is 3.3 GHz without Turbo Frequency, other than that difference between two six core processors is number of PCI Express Lanes the rest of the specification are exactly same.
If we start searching for the benchmarks with best possible scaling on the i7-5930K, then we find that Cinebench 15 runs 14% faster on this CPU, Sysmark Media Creation is about 12% quicker, SiSoft Sandra Cryptography gains an additional 11% and HWPrime gets boosted by 10%. All other benchmarks benefit by between 0.5% and 3.5%.
We also had a closer look at power consumption and in idle we notice that our test setup with Core i7-5930K was burning 6.90% more power than the same system equipped with Core i7-5820K. In case of load power consumption the difference was 3.87%.

4.2 GHz

Overclocking both processors to 4.2GHz basically shows less than 1% gain between the two CPUs as they are both six-core processors and the difference in number of PCI Express Lanes doesn't make any performance gain.
A closer look at power consumption reveals that overclocking these CPUs make for quite a difference. With the Core i7-5930K we see system power consumption rise by no less than 24.47% under load, when comparing with the default power consumption values. In the case of the Core i7-5820K system power consumption goes up by 20.44%, when the CPU is under full load. In idle the differences are 60.29% (5930K) and 72.73% (5820K). 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 2133MHz and 3000MHz with both processors.
Overclocking the system with the Core i7-5930K inside we notice that the performance goes up by 2.03%. In the case of the Core i7-5820K the difference is 2.22% on average. If we go and look out for the benchmarks and programs that benefit the most from increased memory clocks, then we see that 3Dmark 11 Physix performs 7.74% quicker with the memory at 3000MHz and in combination with the Core i7-5930K. In the case of the i7-5820K the same benchmark benefits by 2.43%. WinRAR appears to be scaling excellently on both CPUs whereas the i7-5930K benefits by 7.78% and the i7-5820K by 8.78%. Also the results gathered with SiSoft Sandra Cryptography show 7.80% scaling on the i7-5930K and 8.10% on the i7-5820K. Apart from the applications that show scaling there is also Sysmark, which on average benefits by between two and three percent from the increased memory clocks on both processors.
Looking at idle power consumption, the system with Intel Core i7-5930K turns 11.93% more energy into heat, whereas with the i7-5820K consumption goes up by 9.09%. Under full load the differences are 5.96% in the case of the i7-5820K and 6.84% for the i7-5930K.

Recommendation

The performance differences between the two CPUs we've had a closer look at here are minimal. The reason for that is very simple, since the Core i7-5930K clocks only a little bit higher. If you're thinking about buying a Core i7-5930K over an i7-5820K we would recommend you to do so if you're going to assemble a system which benefits from the full 40 PCIe Lanes. Otherwise spending an additional 182 Euro is simply not worth the 3.66% more performance you get.

Page 1 - Introduction	Page 8 - WinRAR
Page 2 - Sysmark	Page 9 - Frybench
Page 3 - 3DMark	Page 10 - HWBot Prime
Page 4 - XTU	Page 11 - UCBench
Page 5 - Cinebench	Page 12 - Performance Rating
Page 6 - SiSoft Sandra	Page 13 - Power Consumption
Page 7 - Blackhole	Page 14 - Conclusion