I recently bought a PC with an i5 6600k, initially clocked @4.3Ghz.
When I reset the multiplier to standard 39 the system became completely unstable and always crashed within minutes to seconds after boot. (BSODs, Black Screens, Freezes, Reboots)
It took me two days to realise the problem was with the CPU, and I still don't really get it.
At the moment I got 3 ways to run this CPU stable, either deactivate all cores but one. Offset the Vcore for at least +0.025 or set the multiplier to at least 43 which then raises the Vcore in return.
So, how can it happen, that a CPU won't run at stock without overvolting and what would the prognosis for the future be?
Just as a site node:
I did nail it down to the CPU. I switched the motherboard, PSU, RAM combinations, SSD, tried with and without GPU.
Thank you for contacting the Intel community.
In this case, since you have already overclocked your processor any unstable problem can happen when trying to run the processor at stock, you can try making sure the Vcc is between 0.55 to 1.52 which is under the processor specification, you can see this information at the http://www.intel.com/content/www/us/en/processors/core/desktop-6th-gen-core-family-datasheet-vol-1.h... datasheet, see page 112.
Please bear in mind that the CPUs we make that are unlocked and the Intel® Extreme Edition Processors have a manufacturing process that makes them more robust to support customizations. This is because there is a sector of the PC market composed of power users, gamers and computer enthusiasts who want to take the hardware beyond the factory configurations. Intel wants to provide to these people the ability to do so with our processors, but it is pretty known by the industry that any CPU being over clocked will be always at risk and will malfunction sooner or later; they are also pretty aware that they do that under their own risk as the product warranty doesn't cover overclocking.
At this point, I suggest you to also post your inquiry at some of the following websites to see if others have experience similar problems after oveclocking the processor.
http://www.xtremesystems.org/forums/forum.php XtremeSystems Forums
NOTE: This link is being offered for your convenience and should not be viewed as an endorsement by Intel of the content, products, or services offered there.
Please let me know how it goes.