Intel Core i5-6400 vs Intel Core i7-4790 vs Intel Core i5-6600K

Intel Core i5-6400

The Intel Core i5-6400 is a desktop class quad-core CPU. The additional 4 threads are not available to the CPU as it is missing the HyperThreading support. The i5-6400 is based on Skylake architecture and clocks within the 2.7 GHz to 3.3 GHz range. 

Intel Core i7-4790

The Intel Core i7-4790 is a high end quad-core desktop processor using the Haswell architecture. It clocks at 3.6 - 4 GHz and can run 8 threads at once thanks to HyperThreading. Compared to the similar named Core i7-4790K, the 4790 clocks a bit lower and offers no open multiplier for overclocking. The TDP is rated at 84 Watt and therefore suited for Desktop-PCs and large laptops.

Intel Core i5-6600K

The Intel Core i5-6600K is a high-end quad-core desktop processor based on the Skylake architecture, which was announced in August 2015. The CPU, which is manufactured in a 14 nm process, runs at 3.5 up to 3.9 GHz (2 cores: 3.8 GHz, 3 cores: 3.7 GHz, 4 cores: 3.6 GHz) and – contrary to the i7-series – does not support Hyperthreading. Being a so called "K"-model, the Core i5-6600K has a free multiplier and can be easily overclocked. 

Performance

Because of the slightly slower clocks, the smaller L3-cache (6 instead of 8 MB) as well as the missing Hyperthreading support, the Core i5-6600K is about 10-30 percent slower than the top model i7-6700K. The CPU will still handle demanding applications and games without any problems.

Graphics

Graphics are handled by the integrated Intel HD Graphics 530 with 24 EUs (Execution Units), which is clocked at 350 - 1150 MHz. Compared to the HD Graphics 4600 (Haswell, 20 EUs), the performance is increased by around 25 percent. The overall GPU performance is still low-end, so modern games can, if at all, only be played smoothly with low settings. 

Power Consumption

The TDP was slightly raised from 88 to 91 Watts compared to the predecessor.