Power Consumption and Overclocking
The Core i7-5960X is surprisingly efficient given its number of cores. At idle it's no different to an AMD APU and used slightly less power than the 4960X. Under load the 5960X consumed just 4% more power than the 4790K and 4% less than the 4960X.
When it comes to overclocking we know that the original Haswell processors ran hot and results varied wildly from CPU to CPU. The LGA1150 Haswell parts ran hot when overclocked because voltages needed to be increased to at least 1.25-1.30v to achieve a decent overclock.
The much bigger Haswell-E, namely the 5960X, has a significantly larger die. In fact, it's over twice the size in order to house all those extra cores and cache. This lands us at a 140w TDP rating before any overclocking even takes place, so it is hard to know what to expect.
Our Core i7-4790K was a letdown, maxing out at 4.7GHz which was around 300MHz higher than the highest frequency we could achieve on air with the 3960X. Our 4960X also maxed out at just 4.4GHz, so we were hoping to at least achieve that with the 5960X.
Firstly, when it comes to overclocking the Core i7-5960X, throw away whatever air cooler you think will do the job and get a decent liquid cooler. We started with the Silverstone Tundra TD03, an affordable 120mm closed-loop cooler.
After a bit of messing around we found 4.4GHz to be the limit and at this frequency we required 1.30v, which when stress tested using Prime95 caused temperatures to hit over 90 degrees. Some cores got as hot as 95 degrees.
Therefore, we upgraded to the Corsair Hydro H100i which did a reasonable job of getting temperatures under control and when running our assortment of benchmarks temperatures never went above 70 degrees.
For those wondering, before any overclocking took place the Core i7-5960X ran at 72 degrees using the Noctua NH-D15 air-cooler and Prime95 to place all eight cores under full load. Under the same conditions with the same cooler the 4960X was just two degrees cooler, while the 4790K actually ran three degrees hotter.