Overclocking and Power Consumption
We also spent some time overclocking our Core i7-5960X Extreme Edition sample using the ASUS X99 Deluxe. Like most of Intel's processors post Sandy Bridge, new Haswell-E based processors offer limited flexibility when overclocking via BCLK manipulation. If you want to tweak CPU and memory frequencies via the BCLK, it can only be increased by a few MHz at a time before things get wonky.
However, with Haswell-E, additional BCLK multiples or straps are also available. With original Sandy and Ivy Bridge chips only a 100MHz BCLK is available, but with Haswell-E 100MHz, 125MHz, 167MHz and 250MHz base BCLK frequencies are also possible. In addition, like K series SKUs, the Core i7-5960X Extreme Edition is fully unlocked; so CPU, Turbo, and Memory frequencies can be easily altered through multiplier manipulation as well.
With a chip as large and complex as the Intel Core i7-5960X Extreme Edition, power and cooling considerations are very important when overclocking. At its stock configuration the Core i7-5960X is a rated for 140W, but power consumption and heat output can shoot up considerably when the chip is pushed well beyond spec. As such, Intel has incorporated options to increase voltages and specify peak current thresholds too. The new options and power / heat considerations add some wrinkles and complexity to the overclocking process if you're looking to squeeze every last MHz out of a chip, but we still found overclocking Haswell-E to be quite easy and very fruitful.
Our friends at Asus, who have tested a large number of chips, tell us that most Core i7-5960X Extreme Edition processors can hit 4.4GHz with good air or liquid cooling. A large number of the CPUs can hit up to 4.5GHz, and better samples can hit the 4.6GHz mark with the right combination of voltage (1.3v give or take) and a powerful liquid cooler. Although the options are there to disable SpeedStep and various C states, overclocking Haswell-E is really as easy as finding the right combo of voltage, BCLK, and peak Turbo frequencies. By altering those options and leaving SpeedStep, etc. enabled, the processor can still clock-down when not under load, minimizing total power consumption and heat output.
Using a large Cooler Master tower-type air-cooler, we were able to take our particular Core i7-5960X Extreme Edition processor all the way up to 4.6GHz using 1.3v and a peak, all-core turbo multiplier of 46. At that speed, however, we were pushing the limits of the thermal solution as the processor would quickly surpass the 90ºC mark and begin to throttle. With a more powerful liquid cooler, we have no doubt this speed would have been stable with our chip. With our air-cooler though, we had to settle for 4.4GHz.
Overclocking the Core i7-5960X resulted in some huge performance gains in the Cinebench multi-threaded test, as you can see. The performance boost in Crysis wasn't quite as pronounced, but it pushed the Core i7-5960X further into the lead nonetheless.
Before bringing this article to a close, we'd also like to talk a bit about power consumption. Throughout all of our benchmarking and testing, we monitored how much power our Intel Core i7-5960X-based test system was consuming with a power meter, versus other test systems we used for benchmark comparisons on the previous pages. Our goal was to give you an idea as to how much power each configuration used while idling at the Windows desktop and while under a heavy CPU workload. Keep in mind, this is total system power consumption being measured at the outlet and not the the individual power of the CPUs alone.
The Core i7-5960X ended up consuming somewhat less power than the six-core Core i7-4960X under both idle and load conditions, but considerably more than the quad-core Haswell-based processors. The Core i7-5960X's idle and load power was also somewhat lower than the AMD FX-8150, and considering the massive performance increases offered by the Core i7-5960X, that's pretty impressive.
As we mentioned earlier, overclocking the Core i7-5960X can result in large increases in power consumption. To demonstrate this, we also monitored power consumption with the chip overclocked to 4.4GHz (with 1.3v applied). As you can see, power consumption jumped up approximately 180 watts with the chip overclocked. That equates to lots of additional heat, so be sure to invest is a capable cooler if you want to push a Haswell-E to its limits.