Overclocking enthusiast forums and news boards are currently abuzz with word that Intel's Skylake non-K CPUs, i.e. CPUs shipped with locked multipliers, can in fact be overclocked. This previously undiscovered 'feature' of Intel's mainstream CPUs is currently viewed as a bug rather than unannounced feature and may swiftly see Intel's proverbial hammer in retribution, but until that time communities are exploding with unofficial BIOS updates that unlock this feature on selected 100-series motherboards.

The bug, if that is indeed the correct label, surrounds the BCLK. As you should know BCLK overclocking is a Skylake feature absent in Haswell/Ivybridge/Sandybridge, allowing users to push both CPU and memory higher and in finer increments than multiplier-only overclocking. This should only be possible on K-series CPUs such as the Core i7-6700K, but modification of motherboard BIOS's have enabled this feature when even non-K CPUs are installed.

Current implementations of this technique only work when the CPU's Integrated GPU (iGPU) is disabled, thus requiring the use of a dedicated graphics card. Furthermore heat and voltage limitations for these CPUs are unexplored, so you'll want to ensure that your cooler is up to the task and be prepared to swallow the loss if you push things too far.

One supported board is the MSI Z170 XPOWER GAMING Titanium Edition which we reviewed last month. A thread dedicated to overclocking with this SKU on HWBOT is currently tracking 'test' BIOS revisions designed specifically for Intel non-K Skylake CPUs, and results are impressive indeed.



Pepinorang, the Taiwan-based thread creator and Ln2 overclocking enthusiast, has released screenshots of an air-cooled system with non-K Celeron, Pentium, i3, i5 and i7 CPUs pushing 120MHz on the BLCK, resulting in an effective 20% increase in both memory and CPU frequency. Other results are slowly coming in as XPOWER GAMING TE users get their hands on non-K CPUs - models which were until now anathema to overclockers.

Theoretically overclocking non-K series CPUs will be possible on MSI Z170 motherboards with an external clockgen, i.e.:



The news is particularly noteworthy given the substantial price disparity between K and non-K CPUs. Currently OEM Core i5-6600K CPUs retail for ~£190, whilst the lower clocked but locked Core i5-6400 is a little more than £50 cheaper. Similarly the top of the range Core i7-6600K is £60 (~22%) more expensive than its non-K counterpart, which is a pretty penny for an unlocked multiplier. Furthermore 'locked' but overclockable Pentium and even Celeron chips suddenly look like promising targets for hobbyists eager to squeeze everything out of their budget.

Motherboard vendors are currently hard at work developing revised BIOS's that brings BLCK overclocking to non-K CPUs on a wide range of their motherboards. ASROCK in particular are known to be internally validating a BIOS for their Z170 Extreme7+ with the aims of an official release, whilst other manufacturers have even showcased the 'feature' on motherboards with the H170 chipset.

The question now however is if Intel will respond, and in what form that response will take. Given how disruptive this could be to their business model it's possible that they will release a microcode update to once again lock down the feature in non-K CPUs.