Overclocking Experiences and Temperatures
Impressive out of the box performance aside, the other big mystery is how much the new thermal interface and capacitors on Devil's Canyon would change the way Haswell overclocks. I can say, based on my experience with this chip and after talks with motherboard vendors that have used quite a few more engineering samples of the Core i7-4790K, the answer is likely not very much.
Temperatures during load of Core i7-4770K at stock speeds
Temperatures during load of Core i7-4790K (DC) at stock speeds
Both processors were run on the ASUS Z97-Deluxe motherboard with a Corsair H80 self-contained water cooler.
Take a look at the two temperature readings above. Operating at 3.5-3.7 GHz, the 4770K was measuring about 53-55C. While that isn't a bad temperature range, the Core i7-4790K, running at 4.0 GHz, was only measuring at 50-51C. Seeing a couple of degrees improvement in load temperature with an increased clock speed is a welcome change and can be attributed to the improvements Intel designed into Devil's Canyon.
Let's see how the processor overclocks and what that might change.
The overclocking process with the Core i7-4790K is identical to that of other Haswell parts. The theory has been that, thanks to these improved thermals, we should see improved scaling. That did not happen for me. My peak overclock for all cores was 4.7 GHz running at 1.36v and no amount of added voltage or changes to the overcurrent protection or cache voltages, seemed to matter. I could not reach 4.8 GHz for a standard stability run.
To be clear, even for a standard Haswell processor, this result is pretty average. Setting your core voltage to 1.36v is pretty damn high and I've had much better luck with our single Core i7-4770K, as you'll see below. By itself, this does not mean that Devil's Canyon is a worse overclocker, or that it isn't a better overclocker, just that the single sample we were provided didn't show the improvement.
On this same motherboard, on this same day, I was able to take a Core i7-4770K ES processor and hit 4.8 GHz stable with a voltage of just 1.25v. Clearly THAT result is well above average and could be considered one of the better Haswell parts I have seen. So how did the temperatures compare in our best overclocks with the two CPUs?
Temperatures during load of Core i7-4770K at 4.8 GHz
Temperatures during load of Core i7-4790K at 4.7 GHz
Interesting stuff. Even though I wasn't able to get higher than 4.7 GHz, the limit does not appear to be temperature on my Core i7-4790K, just crappy luck. Under load with a voltage of 1.36v, temperatures on Devil's Canyon didn't go past 84C. On the other hand, the original Haswell part hit 91C with a lower voltage (1.25v) and higher clock speed (4.8 GHz).
With just a single CPU sample in my hand its hard to make any definitive statement, but my guess is that the changes Intel made on the Core i7-4790K did in fact have a positive effect on the temperature of the core. It just so happens that our sample from Intel didn't perform as highly as we might have hoped, purely by chance. I am hoping to pick up another 4790K to do some more testing but even then, with a sample size of two, we will be depending on the community to really make the final decision on the benefits of Devil's Canyon.