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i7-7820HQ Lots of Cache L2 errors with undervolt

RaZoRbel

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The device in question is ThinkPad T460P with i7 7820HQ motherboard from T470p. Boards are interchangeable, and everything works fine with stock voltages.
Undervolting, however, gives very strange results. -0.085 CPU/Cache is stable on idle and in Cinebench R23, and the scores improve a lot thanks to lowered wattages/temps. No cache errors to be seen in those scenarios (idle, light load or stress test with CB).
However, heavy games like BeamNG.drive or Metro 2033 throw a lot of WHEA Cache L2 errors in HWinfo. What's strange about those errors is that 9/10 times they will appear like 100 at once, and after that they can add up by 2-5 every minute, or by 100. Without any crashes.
And once a single error shows up they will start popping up even I close the game and leave the laptop on desktop. To add more to the strangeness is that if I remove the undervolt by setting it to 0, the errors would still add up.
The only cure is to powercycle the system, and then the errors won't show up.
Lowering the undervolt to 0.056 seems to slightly delay the time it takes for heavy games to bring the first errors (or maybe it's a placebo)
Judging by the graph in HWinfo those errors tend to appear when there is big voltage/load/frequency spike. I've tried to set cache ratio to a smaller value (like 30), but this setting doesn't seem to work.
Am I that unlucky with the CPU lottery or is there something wrong with my settings/windows setup?
P.S. Could not fresh install of windows be the problem? I'm running the same installation that was used with original T460p motherboard (which had an i5 6440HQ with a successful stable undervolt of -0.153). I've deleted throttlestop.ini to reset the settings when I've replaced the motherboard.
 

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Most people do not undervolt the Intel GPU, the iGPU Unslice or the System Agent.

WHEA Cache L2 errors in HWinfo
When all of the offset voltages are set to 0, are there any WHEA errors? You can also use ThrottleStop to lower the FIVR Cache Max value to slow down the cache. That might help reduce these errors.

errors tend to appear when there is big voltage/load/frequency spike
Lowering the AC/DC loadline values can help minimize voltage spikes. The BIOS of most laptops do not have access to this very important setting.

I remember when the 11th Gen was released, people on overclock.net said that Intel had fixed the problem with WHEA errors that were being caused by some games. I am not sure how far back this issue went. If 10th Gen had this problem then it is possible that your 7th Gen has the same problem. I have never heard anyone in the TechPowerUp ThrottleStop forum mention this issue.

Do a Google search for overclock.net and WHEA error and you should find lots of relevant info.
 
reduce the undervolt.
 
reduce the undervolt.
That was my suggestion.

When all of the offset voltages are set to 0, are there any WHEA errors?

For some Intel CPUs, even when you are using default voltage, there are still some recent games that will cause WHEA errors. These errors are being corrected in real time so they typically do not cause the CPU to freeze or crash. A properly functioning CPU should not be producing any errors like this. Not sure why modern games can trigger WHEA errors.
 
Most people do not undervolt the Intel GPU, the iGPU Unslice or the System Agent.
GPU undervolt of -0.096 lowered GT Cores Power by around 1-3w on my previous motherboard with HD530. Stress-tested it with FurMark and many hours of WoT Blitz, and no crashes/errors have been encountered. I haven't tested the power usage on newer board, but FurMark seems to be stable on -0.096.
As for iGPU Unslice - H264/VP9 1080p60 videos doesn't crash the browser so I've decided to stick with it. To be fair, I don't know if this bring any wattage benefit. Same goes for System Agent. Don't know about the benefit, but it seems stable. (The value for System Agent was found somewhere on Reddit, was successfully tested on 6440HQ and transferred to the new board).
Just to be clear, iGPU, Unslice and SA undervolt have no influence on my WHEA Cache errors.
When all of the offset voltages are set to 0, are there any WHEA errors?
No.
You can also use ThrottleStop to lower the FIVR Cache Max value to slow down the cache. That might help reduce these errors.
Sadly, that didn't help( I've even tried to limit both Min and Max values to 10 and 30.
reduce the undervolt.
That was my suggestion.
Reducing the CPU/Cache undervolt to -0.045 seems to fix the problem with cache. 30 minutes of Metro 2033 didn't bring any errors.
So I guess I'm just that unlucky with my CPU. Most guides and reports on Reddit suggest that 6-7gen HQ chips can easily accept at least -0.100mv.
Thanks unclewebb and GerKNG for your help!
 
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