The
i5-6600K is based on
Skylake architecture while the
E5-2651 v2 is based on
Ivy Bridge.
Using the multithread performance as a reference, the i5-6600K gets a score of
209.3 k points while the E5-2651 v2 gets
426.2 k points.
Summarizing, the
E5-2651 v2 is
2 times faster than the
i5-6600K . To get a proper comparison between both models, take a look to the data shown below.