Finally we also tried to overclock both the Core i9 7980XE as well as the Core i9 7960X as far as we could. For these tests we had to use the ASUS ROG Rampage VI Apex motherboard, considering the power circuits on "regular" X299 boards cannot withstand 16- and 18-core CPUs on maximum overclock. Overclocking on other X299 boards often resulted in lower instead of higher scores due to throttling. For overclocking we used a custom water cooling set-up with an EK Supremacy block and a 480mm radiator.
Using the 7960X we were able to achieve an overclock with all cores active of a maximum of 4.7 GHz, with a Vcore of 1.2V. This results in a Cinebench 15 score of 4073 points, 33.7% higher than the regular score. Unfortunately the power consumption of the system goes through the roof: we measure 540 watt for the entire system, whereas we measured 244 watt using the standard clock frequency. This means 2.2x as much power consumption for a performance increase of a third.
We also need 1.2V Vcore with the 7980XE in order to achieve the maximum clock frequency. Due to the extra cores we are limited to 4.6 GHz here. This results in a Cinebench 15 score of 4431 points, 32.5% higher than the regular score of 3342 points. The power consumption? Do not freak out: a careless 550W for the entire system, while it ends up at 280W with the standard values.