Core i7-4790K overclocks about as well as we expected

Quizzical

http://hardocp.com/article/2014/06/09/intel_devils_canyon_good_bad_ugly

Which is to say, not very.  HardOCP was only able to overclock it to 4.7 GHz, from a stock turbo speed of 4.4 GHz.  Now, a 4.7 GHz Haswell chip is very fast--as is a 4.4 GHz Haswell chip.  So it's still the fastest quad core chip on the market.  But it never seemed plausible that a marketing refresh would suddenly make one bin of a chip overclock much better than before.

I think the point of the Core i7-4790K is that if you want overclocked performance without having to overclock it yourself, Intel will cherry-pick chips that overclock well and give you a moderate overclock of the chip.  They do this for the Core i7 version, but notably don't do this for the Core i5 version; the turbo speed difference between the two is 400 MHz, as opposed to the usual 100 MHz or so.  Intel is trying to give people who don't care about hyperthreading a reason to buy a Core i7 over a Core i5.

Still, as HardOCP noted, with a normal Core i7-4770K (or Core i5-4670K), it's hardly guaranteed that you could reach 4.4 GHz even with an aggressive overclock and a good cooler.  And to have the aggressive clock speeds fit into an 88 W TDP is impressive.  If you're an overclocker looking for a miracle chip that overclocks as well as Sandy Bridge, this isn't it.  But if all you want is the fastest quad core you can buy and are willing to pay a significant but hardly outrageous premium for it, and you aren't into frying chips by overclocking them yourself, then the Core i7-4790K just might be for you.

I'll add that I'd regard it as unlikely that the top bin of Broadwell will be as fast as this, so this could be easily be the fastest quad core chip on the market--as well as the fastest in single-threaded performance--all the way into 2016 or longer.