6850K Overclock breaks after 2 years

[Samuel]

I have had my 6850k running at 4.2Ghz @1.29v on a Asus x99-A II motherboard for over 2 years with no problems, I was running the Timespy benchmarks yesterday and several runs where fine then the cpu score dropped a few hundred points, I checked and the 6850k was running at 3.8Ghz on all but the 6th core which was running at 4Ghz. I have tried clearing the bios, changing to a different bios, even reinstalling windows to fix this but even though the overclock shows in the bios the multiplier doesn't seem to hold when windows boots up and it always reverts to 3.8Ghz on the first five cores and 4Ghz on the sixth.
Also to add to my confusion within windows I can use Intel Extreme Tuning Utility get the 4.2 overclock back but it looses it as soon as windows is restarted.
This shouldn't have been a heat issue, I have a H115i and the temps rarely hit 60c. I reverted to 3.8GHz across all the cores and it is perfectly stable. If I can't fix this it might give me an excuse to buy a new z390 mobo and the 9900k whenever it is released.

 

[Davva2004]

Silicon ages over time, especially when CPU’s are overclocked.

 

[WYP]

Your silicon may have degraded a little over the years. It probably needs a higher voltage now to maintain 4.2GHz.

 

[AlienALX]

It could be a whole wealth of factors.

1. Silicon degradation.
2. VRM degradation (the most likely culprit)
3. Spectre patches, or some sort of BIOS change.

 

[Flux]

Just found this on hexus . net

Windows 10 KB4100347 update breaks Broadwell-E overclocking

Did you install the KB4100347 update?

Might be worth looking into.

 

[AlienALX]

Yup definitely. I'll need to check that myself tbh, given both rigs I use are BE and overclocked lol.

 

[Dark NighT]

I will have a look tomorrow to see if i got it installed but so far my oc is holding up just fine.

 

[Samuel]

Fixed!!

That fixed it I uninstalled that update and the overclock if fine now, stupid windows breaking a perfectly good overclock. Thanks a lot for the help.

 

[Dawelio]

That fixed it I uninstalled that update and the overclock if fine now, stupid windows breaking a perfectly good overclock. Thanks a lot for the help.

It wasn’t Windows that broke it, it was the update for windows.

 

[Flux]

Glad its working now

 

[AlienALX]

It's a Spectre patch, so I was correct. These patches close off junctions in the CPU and make them function differently, so I would imagine that is why they make OCs unstable.

 

[Dark NighT]

Bit of a bump but yeah after reinstalling a new windows 10 it turned out the newly tweaked microcode released a while back shaved 400mhz of my OC on my i7 6800k, did some research and managed to find a somewhat tricky solution but works fine, replaced a Dll without the microcode stuff and my oc was back.