Overclocking Intel processors by messing with the base-clock (BCLK) has been pretty unstable since Intel fully integrated the core logic (northbridge) with its processors. It was unstable as it was used for other key components on the chip like the iGPU and PCIe root-complex. With Skylake, Intel has de-linked the base-clock from other clock domains, which allows for overclocking using the BCLK. This is very helpful with overclocking on non-k processors.
Surprisingly some of the first motherboards to enable BCLK overclocking on Skylake processors come from Supermicro. Overclocker “Dhenzjhen” using a Supermicro C7H170-M motherboard was able to achieve a 5.00 GHz overclock on a Core i3-6320 dual-core chip. Keep in mind this processor has a base clock of 3.9 GHz.
Since this news broke both ASUS and ASRock have been working on getting BCLK overclocking to work on non-K processors. ASRock had contacted Anandtech and shared CPU-Z screenshots of a locked Core i5-6600 running at 4.5 GHz on the company’s Z170 Extreme7+ motherboard. ASRock was able to achieve this with an experimental BIOS. Overclocker elmor was able to take a Core i3-6300 to an astonishing 5.8 GHz on an ASUS Maximus VIII Gene.
I would expect all the major motherboard manufactures to push out new BIOS updates that enable BCLK overclocking in the next few weeks.