Power Consumption & Overclocking
Measuring at the wall via a Kill-A-Watt meter, we get the above results. Both systems pull a healthy 291 Watts from the wall at full load at stock speeds, and 93 and 96 Watts respectively at idle.
Starting out at stock speeds of our two CPU’s, the i9-7960X and i9-7980XE, we set out to see how far we can push the clock speeds.
Most serious overlocking enthusiasts do all of their overclocking from the BIOS, and that’s exactly where we head to push the CPUs to their breaking point. We adjusted the line load calibration to its stiffest setting to maintain CPU voltages under heavy overclocking loads, in this case, ‘Level 1’ which rigidly
maintains exactly the same voltage all the time. I started bumping up the multiplier and then the core voltage when it became unstable.
Overclocking the i9-7980XE
Even though the base clock speed is 2.6GHz, the CPU cores spend much of their time bouncing around the 3GHz range at idle due to Turbo Boost helping out the miscellaneous tasks Windows 10 is always chewing on in the background. Here we happened to snag a screenshot while it was hovering at 3.4GHz on the core we were monitoring.
Moving in small steps since we expected to reach issues at a much lower clock speed, we kept bumping the multiplier higher and higher, we a reboot and test each time. Our test motherboard kept up with core voltage until about 4.4GHz where we had to manually take control of the voltage to carry on. In the end, we were able to reach a multiplier of 46 across all cores, and then nudge the base clock up to 101.1MHz to give us a staggering 4.65GHz at 1.26v.
You might be used to seeing clock speeds over 5GHz with some recent Intel CPU’s, but you have to keep in mind this is four and a half times as many cores, all at the same time. Intel does give you independent core overclocking, you can adjust the multiplier and voltage of each core fully independently. It would take some time to do, but you could overclock one core at a time for maximum performance. We were able to easily take a few of our strongest (and coolest) cores to more than 4.9GHz.
Considering our stock Cinebench score was an already awesome 3329 CB, pushing this CPU to over 4.6GHz nets us a whopping 4473 CB. With our ram overclocked from 3200MHz to 3733MHz, we were able to achieve our best single socket score ever of 4506 CB.
We had our power meter still connected for this test runs and clocked a staggering 705 Watts drawn from the wall while overclocked. If you subtract the idle load, this means the CPU was responsible for approximately an additional 600W of power draw. This will be given off mostly as heat, so keep in mind you need an incredibly powerful cooler to handle this. Our test bench was outfitted with a powerful 240mm based custom loop, but even it would struggle to maintain good temperatures for more than a few minutes of continuous use at this load. We saw the hottest cores peaking at around 96C during these overclocked runs, with the cooler cores in the mid 70’s and an average of around 85C. This is an immense amount of power and we highly recommend a high-performance liquid cooling system as a bare minimum if you plan to push the clocks.
Overclocking the i9-7960X
Moving in small steps since we again expected to reach limits at a much lower clock speed, we kept bumping the multiplier higher and higher, we a reboot and test each time. Our test motherboard kept up with core voltage until about 4.4GHz again before it got too high (and too hot) where we had to manually take control of the voltage to carry on. In the end, we were able to reach a multiplier of 47 across all cores to give us an impressive 4.7 GHz at 1.27v across all sixteen cores.
The CPUz screenshot shows something I wouldn’t have guessed possible on water cooling. Sky Lake has proven to be a good overclocker, and this trend has carried on into the HEDT realm, even to the top CPU’s this generation.
Considering our stock Cinebench score was an already awesome 3168 CB, pushing this CPU to 4.7GHz nets us a score just over the 4000 point threshold. With our ram timings tweaked, we managed to nudge the score up to 4063 CB.
As with our i9-7980XE CPU, power draw while overclocked was monitored and hit approximately 675 watts from the wall, or about 575W worth of CPU load. Again we saw the hottest cores peaking at around 95C during these overclocked runs, with the cooler cores in the mid 70’s and an average of around 85C at these settings. Given we have 16 cores pushing the 5GHz mark; we find this power draw and heat output pretty reasonable.