Intel only launched its Skylake-based Core i7-6700K processor just recently, with a professional overclocker already pushing it up to just under 7GHz, sitting at 6998.88MHz.
The achievement was done using an ASRock Z170 OC Formula motherboard, where Hong Kong overclocker Chi-Kui Lam used an engineering sample of the Core i7-6700K, an overclock of 74.9% from its stock frequency of 4GHz. G.SKILL provided the RAM chops with Ripjaws 4 DDR4 RAM, alongside a 1300W PSU. The processor was keeping cool under LN2, which is normally required for these insane CPU overclocks.
The Core i7-6700K at 6.9GHz was only on a single core, with the other three physical cores and the four Hyper-Threaded cores being disabled. So we're looking at a single-core 6.9GHz, which had its voltage cranked up to 1.88V, compared to the 1.2V on the stock CPU.