Intel Undervolt Protection

[TwistedAndy]

A few months ago Intel introduced a new feature called Dynamic OC Undervolt Protection, which may completely block the undervolting on Intel CPUs.

It works in conjunction with recent microcode updates and can be enabled by a motherboard vendor.

In other words, ASRock, Gigabyte, Dell, HP, or any other vendor may decide to disable it by default to sell you a more expensive motherboard.

If the undervolting protection is enabled, you can't decrease the voltage even if you have the unlocked CPU and use the top Z-series chipset. The negative voltage offsets you specify in BIOS, Intel XTU, ThrottleStop, etc. will be ignored.

This feature is described in the latest Intel Software Developer's Manual (December 2022, Volume 4, 2-17) and controlled by the read-only 0x195 MSR called IA32_OVERCLOCKING_STATUS.

You can check whether this feature was enabled using the latest version of the HWiNFO64 utility. It is called Dynamic Overclocking Undervolt Protection.

Unfortunately, I can't find this setting in the decompressed BIOS of my Dell XPS 17 9720 with 12900HK, but I hope Dell and other vendors will add it in the future.

Also, I would like to hear any suggestions how to disable this "feature". I need to find the way how to modify the R/O 0x195 MSR.

 

[unclewebb]

Thanks for posting that information. That will allow me to report in the ThrottleStop FIVR window when Undervolt Protection is enabled.

Unfortunately, MSR 0x195 is a read only register so it will never be possible for ThrottleStop to toggle this feature off. I do not think Dell will ever provide a simple BIOS option to disable Undervolt Protection.

If this is part of the most recent microcode then this will likely put an end to undervolting for all 12th and 13th Gen CPUs, desktop and mobile. The end of an era.

 

[TwistedAndy]

Which is even more interesting, many modern motherboards have a setting called Undervolt Protection, but it controls a completely different thing: Intel CEP (Current Excursion Protection). Even Dell Precision 7670 and 7770 have it. From my perspective, CEP is the real protection and not the lock.

As a result, we may see messages like "I have disabled the Undervolting protection, but undervolting is still not working".

The other confusing part is that the new lock can affect earlier CPUs if a vendor decide to update BIOS for old devices.

 

[unclewebb]

the new lock can affect earlier CPUs

MSR 0x195 does not exist in my 10th Gen 10850K desktop CPU. I think this new undervolt protection only applies to 12th and 13th Gen.

 

[TwistedAndy]

It appears, that the problem with the new Intel Undervolting Protect feature is much deeper: Inter Undervolting Protection: The Whole Story