Intel has identified an issue that potentially affects the 6th Gen Intel Core family of products. Heres what Intel has to say about the Skylake issues that happen in Prime95:

We haven’t heard of any motherboard vendors to roll out the UEFI updates with the Intel fix incorporated just yet, but they are coming soon and we suggest keeping an eye out for your particular motherboard model. Since the fix is in the UEFI and there are hundreds of boards on the market, it means that Intel will need to work with each and ever one of its board partners to release a microcode update for all the impacted boards. Intel discovered and released a fix for the bug that is placed in the UEFI/BIOS of the motherboard the Intel Skylake processor is being used on. It is possible that Skylake processors could be having issues with other complex compute heavy workloads that are used in say the scientific and financial industry.

Intel has confirmed that its Skylake processors are suffering from a fixable bug that can cause a system to freeze when performing complex workloads. The Skylake processor bug is reproducible when using the Windows and Linux operating systems. The mathematicians and community over at found a bug in the new 6th Generation Intel Core ‘Skylake’ architecture that freezes any system that has a Skylake processor in it when running the GIMPS Prime95 Advanced Exponent test.

Intel processor diagnostic tool freeze