Overclocking The 6950X and Power Consumption
We also spent some time overclocking our Core i7-6950X Extreme Edition using the MSI X99A Gaming Pro motherboard. Like most of Intel's processors post Sandy Bridge, the easiest (and sometimes the only) way to overclock Broadwell-E is by tweaking various multipliers. BCLK straps and granular frequency manipulation are also available for fine tuning, but the biggest gains will come by upping the CPU core voltage and cranking up the CPU's multiplier. Like more mainstream K series SKUs, the Core i7-6950X Extreme Edition is fully unlocked; so CPU, Turbo, and Memory frequencies can be easily altered through multiplier manipulation.
With a chip as large and complex as the Intel Core i7-6950X Extreme Edition, power and cooling considerations are very important when overclocking. At its stock configuration the Core i7-6950X 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 threshold 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 an Extreme Edition chip, but we still found overclocking Broadwell-E to be quite easy and very fruitful.
With proper cooling and a moderate voltage bump in the 1.3v - 1.35v range, we suspect many Core i7-6950X Extreme Edition processors will be able to hit 4.3 - 4.5GHz with quality air or liquid cooling. With more powerful cooling and some additional voltage though, we're certain high clocks will be possible. Although the options are there to disable SpeedStep and various C states, overclocking Broadwell-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 Arctic Cooling tower-type air-cooler, we were able to take our particular Core i7-6950X Extreme Edition processor all the way up to 4.5GHz using 1.35v and a peak, all-core turbo multiplier of 45. 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 ratcheted things down a bit and settled for 4.3GHz with 1.295v. With those settings everything was stable, but under sustained load, temps would just begin to tickle the 90ºC mark.
Overclocking the Core i7-6950X resulted in significant gains in the Cinebench multi-threaded test, as you can see. The performance boost in Crysis was also fairly pronounced.
Before wrapping things up, 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 i7-6950X-based test system was consuming with a power meter, versus the other test systems we used for benchmark comparisons. 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.
Despite having more cores than the Haswell-E based Core i7-5960X, the newer Core i7-6950X consumed a similar amount of power at idle. Under load, however, the additional cores on the 6950X (along with the higher clocked memory) pushed it about 50W higher than the 5960X. However, the Core i7-6950X's power consumption was still significantly lower than AMD's fastest desktop processor and was in the same ballpark as the FX-8370 under load.
As we mentioned earlier, overclocking the Core i7-6950X can result in measurable increases in power consumption, as is the case with other processors as well. To investigate this, we also monitored power consumption with the chip overclocked to 4.3GHz (with 1.295v applied). As you can see, power consumption jumped up approximately 35 watts with the chip overclocked. That equates to additional heat output, so be sure to invest in a capable cooler if you want to push a Broadwell-E chip to its limits.