How to reenable undervolting in 2020 Dell Laptops by editing EFI variables | Hacker News Reader

How to reenable undervolting in 2020 Dell Laptops by editing EFI variables

brendangreenley.com

62 pointshmm3716 comments

This method works because many system bioses apparently just hide many setup options, and therefore if you can find these options, you can flip the switch by editing EFI variables. Doing so isn't that difficult as the blog entry states.

So this method could also work for many other different laptops to reenable undervolting or overclocking, etc.

You can actually brick a system if you put the wrong values in EFI. Linux even has put safeguards in place to avoid doing this with a `rm -rf /`.

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin...

Yes I think that's possible, and then you would need to get e.g. a 8 pin bios programmer for $10-15. But... I think often times if a switch wasn't supposed to be flipped you could just yank the battery to try resetting the bios to default settings. But I don't know or rather I don't have much experience with this.

I actually posted this because I just found out about this, and I didn't know you could do this in the first place and was wondering what others thought, or if they tried this before. I just tried this on a 2020 Dell laptop using linux since all the tools are actually on github. I haven't checked yet if it could be now undervolted but everything seem to work correctly.

If it works I was also thinking about trying to edit the fan curves as well because there was actual variables for the temperatures that you could edit as well. That way you don't have to rely on dell-bios-fan-control programs, etc.

Pulling all of the batteries is unlikely to unbrick anything if Linux allowed write access to critical system-specific manufacture variables most users of other operating systems typically don't obliterate randomly. UEFI variables are typically stored in SPI EEPROMs, not battery-backed SRAM as ancient CMOS clock and BIOS data was.

and that seems to be kindof a problem? in so far as possible, hardware should attempt to be unbrickable

I'm rewriting an embedded BIOS for an Intel processor at work and It's been a bit of a clicking point for me about how modern X86 really works. Nothing EFI or the like, but still very instructive.

Now if only I could get DCI to work...

Can you share more about what your work is? Why re-writing - makes it sound like there's an existing BIOS that doesn't work?

What's different about modern x86 compared to the old standards?

This is a good watch, it goes into detail on the architecture of the PS4 showing how it differs from a standard x86_64 “PC.”

https://youtu.be/QMiubC6LdTA

The “too long; didn’t watch” summary is that there’s several peripherals, timers, RTC, etc outside of the processor that software will expect to be present (or at least emulated) with specific interfaces. You can implement x86_64 without a lot of this, or redone in a more modern style, but software such as a Linux kernel will have to be patched for it.

Typically a modern laptop will have all the legacy peripherals emulated, and the modern peripherals will live alongside them.

I followed a similar technique to undervolt an Acer Predator with an i7 11800H processor by -100.06 mV.

And the result was a 15 celsius reduction in average CPU temperature and improved performance, incredible. I can rarely hear fans now.

I wonder why isn't this the norm. Perhaps some chips become unstable?

This is the guide I followed on Youtube: https://www.youtube.com/watch?v=X_OFOmfjs6k

And here is a relevant screenshot of the bit to be flipped in the video: https://i.imgur.com/xsG0jSE.jpeg

Intel chips in particular vuln to issue when under volted (mentioned in post)

https://archive.is/4Mtnq

The wired article also mentions it is patched though. So maybe it has to do with avoiding a “non advertised throttle” lawsuit.

Thank you! This is why we can't have nice things.

Many intel laptops could be improved significantly. But because a few could exploit that, many have to pay the price of hotter, noisier, less powerful and less energy efficient laptops.

I guess I'm not interesting enough for hackers to mess with processor voltage so I'll keep it quieter. Or perhaps it was indeed patched.

I use TPFanControl and ThrottleStop on a T480. Without it, there is a pathology where it gets stuck in an upper frequency limit of around 900 MHz when it should peak to around 4 GHz (although the official Turbo Boost speed is 3.4 GHz).

word of caution - better have a secondary computer and easy access to bios programmer before doing this.

just downgrading bios (supposedly supported by the laptop manufacturer as an option in the bios) bricked a laptop of mine and it required scouring the internet to find the solution.

it is a shame that despite all of this you still are dependent on the os and its ecosystem to apply the undervolt. disabling virtualization and wsl is a very poor sacrifice for letting throttlestop work.

editing EFI variables would be worth it if it could allow you to apply undervolting right then and there!

Is it also feasible on AMD platform? I have an embedded board with Ryzen 3200G that does not allow over/underclocking I would be interested in getting it to work there.

There's UMAF_SMOKELESS which I think is an alternate bios allowing some of this for amd in general. Universal X86 tuner also can help with setting power limits.

> And unlike Intel laptops of the past, many in 2020, including the XPS, Vostro, and Inspiron, have undervolting disabled by default due to the Plundervolt vulnerability.

Aaand SGX is now deprecated. Therefore, almost useless technology (aimed at big guys who would want to have a safe space protected from computer users and owners) prevents useful one from working. Keeping priorities straight!

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