Overclocking
I really wanted to test ASRock's claims here with the X299 Extreme4, and I could not be more pleased with the result. Overclocking was easily done, and the voltages I needed to adjust were easily adjusted as well, with hardly a fuss. Being able to push all 18 cores of my 7980XE CPU to 4.6 GHz is no small feat, but the seemingly simple X299 Extreme4 did so without any problems at all. Because I am using an AIO cooler, I do have an additional fan strapped to the system by the VRM cooler, which improves its cooling ability for sure; however, this should be a standard thing for watercooling users to do these days. In the end, I'm not sure if I am more impressed with the CPU or the board... however, both deserve some praise here.
The ASRock X299 Extreme4, when you start changing options, boosts input voltage up to 2.1 V from the "standard" 1.8V a stock-clocked CPU requires. This immediately results in a huge increase of heat if you do not take the time to manually adjust this voltage to your CPU's exact needs. What voltage you are going to need for this particular option is going to vary from chip to chip, so some testing is in order on any of the ASRock X299 motherboards, and the X299 Extreme4 is no exception. While I understand why ASRock has the board do this, I really would prefer if it didn't.