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Question Overclock gone bad after CMOS reset

Grimnir

Junior Member
Jun 8, 2020
8
1
11
Hey y'all,

I have encountered a really weird issue that I hope you can help me with, or at least explain.

Because of a bug in my motherboards BIOS I had to reset CMOS. This in itself is unrelated to the problem, it was only that I had disabled CMS which gav the fun little bug of not having a display during the boot process. So, I had to disconnect the computer, move it to a table in another room, remove the graphics card and pull out the battery. So, yeah, that was fun.

I used protection, of course. Always use protection.

Booting up the computer after this was no problem. However, booting up with my previously saved profile failed: "Overclocking failed or somesuch - do you want to load optimized defaults or keep settings and enter BIOS?". Something like that. This is with an overclock that's been rock solid for 2 years.

Only after going from 5Ghz to 4,8Ghz and reducing the memory speed from 3800Mhz to 3200Mhz did I get it to behave more reasonably (with slightly lower voltage and LLC). This was still not stable though. Tried Prime95 and OCCT. They crash after about 15-20 min. Not even with a nice little BSOD, Windows just freezes and I have to go for the power button. Oddly enough OCCT doesn't even report any errors up until then, which it otherwise tends to do if the overclock is unstable and the CPU needs more voltage.

I've tried updating the BIOS to the latest version but it's the same thing. Optimized defaults seem stable though but I haven't had the time yet to do proper testing, just an hour and a half with OCCT. I'll get to some more testing after work.

Anyhow, the TLDR-version: What the hell is going on here? I've been running 5Ghz stable for two years. The same settings could almost run 5,1Ghz stable. Now 4,8Ghz is unstable, which should be a walk in the park.
Just a few days ago I got a new case so I've moved all components and done thermal/stress testing after that. No issues whatsoever. But now, after resetting CMOS, it's gone bananas.

Do you have any idea of what's the matter here? What could have gone wrong?
 

DrMrLordX

Lifer
Apr 27, 2000
16,041
5,000
136
Hmm I would leave this one of the Coffee Lake experts, though I have to wonder - are you sure you set everything exactly the same as before? Seems like something like LLC settings or VRM frequency modifications could have helped stabilize your old OC.
 

Grimnir

Junior Member
Jun 8, 2020
8
1
11
Hmm I would leave this one of the Coffee Lake experts, though I have to wonder - are you sure you set everything exactly the same as before? Seems like something like LLC settings or VRM frequency modifications could have helped stabilize your old OC.
Yeah, I saved my BIOS settings and loaded them after resetting CMOS. Also noted all of the settings before updating BIOS so I could restore them.
 

Grimnir

Junior Member
Jun 8, 2020
8
1
11
After sort of testing the computer piece by piece it's almost back to normal. It's like suddenly the CPU decided to behave again, and when I incrementally raised clock frequency and voltage, it was just back to being the same good old chip again.

I mean, before I was unstable at 4,8Ghz at 1,32Vcore. Then suddenly I could run 4,8Ghz, and 4,9Ghz, at 1,28Vcore. No I'm running 5Ghz at 1,33Vcore, exactly as I used to except I can do that with a less aggressive LLC.

One thing that's not back to normal though, is my RAM. I've ran it overclocked at 3800Mhz CL16. Now I can run it stable at 3700Mhz Cl16 and tighter sub-timings. Going for 3800Mhz is like hitting a brick wall.

At 3700Mhz CL16 I can run it at 1,35V and VCCIO/SA at stock settings. I've tried 3800Mhz at 1,45V and VCCIO/SA at 1,25V, but I can't even boot with that.
 

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