Update – April 22, 2020 @ 17:00
As suspected, Intel’s 10th-gen Skylake-based (6-8 core) chips in laptops are shipping with undervolting abilities disabled from some (if not all) OEMs. Well-known tech YouTuber Dave Lee reviewed his loaned MSI GS66. Among his criticisms were the build quality, price, and lack of ability to undervolt.
Until OEMs and Intel find ways of mitigating “plundervolt” without disabling a key feature of the chip that has become crucial on today’s thin, light, and undercooled notebooks, I cannot recommend purchasing any 10th-gen-equip systems if efficiency or performance are your main concerns.
Hopefully Intel will be able to produce a proper fix for this vulnerability that does not involve disabling undervolting, or I suspect they are going to lose even more market share to AMD.
Note: There is some great information linked in the comments regarding EFI modifications, so please check that out if this method does not work. Original post below:
I noticed that the temperatures on my XPS 15 7590 had been going crazy as of late. Instead of peaking at around 87C during mixed usage, I was seeing temperatures hitting 100C. At first I thought I had been the victim of rabbit hair and dried-out paste and so disassembled the laptop for a cleaning. After cleaning and repasting, however, my temperatures were still hitting 100C.
“That can’t be right”, I thought.
I checked my Throttlestop settings more closely, and lo and behold, my undervolts were all listed as 0.000mv. I recalled someone in my comments here on the Throttlestop guide had expressed a similar issue on their Dell G3 laptop, and then I remembered a security vulnerability that Intel had announced a few months back — then everything clicked. Dell must have silently pushed a BIOS update through Windows Update that disabled undervolting to mitigate the Plundervolt vulnerability.
Before we get into how to roll back the BIOS and re-enable undervolting, we should address whether undervolting actually needs to be disabled or not. The security exploit requires physical access to the machine, and so I think for nearly all home users, that already makes this something you do not need to worry about (enterprise might be another story, though). Intel left it up to the manufacturer for how to address this issue, and Dell cheekily decided they would push a BIOS update over Windows Update without telling anybody. That would be fine if undervolting wasn’t a literal necessity on the XPS 15 due to its thermal limitations.
So, how to fix this? Regardless of your manufacturer, you’ll need to find the next most recent BIOS update, download it, and re-flash the BIOS. For the XPS 15, that’s 1.5.0, but you can generally find this by looking at the most recent BIOS update listed on your OEM’s website, and lowering that number by 1 integer (e.g. if the most recent BIOS that disables undervolting is 1.9, try to look for 1.8).
You can’t just install the update and be done with it on the Dell, though. After the update finishes, press F2 to go directly to your BIOS settings. Here, you’ll need to reset the settings to the BIOS defaults. If you don’t do that, undervolting will not be available.
There’s one more thing you’ll need to do, which is disable for the ability of the BIOS to be updated through Windows Update again. Under the “Security” tab, look for the option “UEFI Firmware Update Via Capsules” and turn that off.
Once done, you can restart and your undervolt should be working again. Be wary of any additional BIOS updates, as they will almost certainly remove your ability to undervolt, and perhaps even re-flash.