Originally posted by andrei_me
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Linux Developers Discussing Possible Kernel Driver For Intel CPU Undervolting
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I'm using "intel-undervolt" on my laptop and it's working just fine. I'm not on that machine right now so I can't confirm that's the name. I think I have a stable -90 mv undervolt working in Linux on my Lenovo Legion 7i. Unfortunately, audio output from the built-in speakers still doesn't work, but that's a separate topic.
If there's a more... "official" or "endorsed" way via the kernel, I'd be happy with that too I suppose.
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I have no idea whether he reads on Phoronix, though I do not believe he has an account on the forums, even if he does read here.
I'll try asking him about this.
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I have a lot of experience with dynamic undervolting in microcontroller electronics. It is a very lucrative endevour for battery powered devices, but it does require a bit more engineering time to make sure it all works safely without data corruption. In my case, I was able to improve my application running for a few hours on a single NiMH AA to being able to run for several days!
Most of my power savings revolved around undervolting an SD card. My app required bursts of data from the card on a regular basis, but in between bursts of data, there was silence. Originally I thought I would just completely power down the SD card between bursts of data, but that turned out to be a no-go because the SD card requires quite a long boot up time before it can be accessed again.
However, during periods of no activity, you can often safely undervolt a device and it will retain it's current existing state okay. When you need to communicate with it and make it do active work, you need to bring the voltage back up before you start doing anything, else you'll lose state and corruption results (not to mention the difficulties in dealing with wrong I/O voltage thresholds if you're undervolted). In my case, waiting for the voltage to rise was a lot less time and electricity wasted than waiting for the SD card to boot back up from zero, so undervolting really helped a lot for me.
You can get some interesting compounding benefits from reducing power consumption. Obviously, reduced power means less heat produced, so if you get low enough you end up not needing to power on cooling fans, which saves more power. But in my case, there was another interesting effect in that once I got down lower and lower in power consumption, the internal resistance of my battery became less and less and the efficiency of my switching power supply got better and better, which really helped extend my run times even further. It was great! I remember at one point making a small optimization to my code and finding a much greater improvement in run time than I was expecting, due to the compounding benefits in efficiencies elsewhere.Last edited by ed31337; 21 October 2020, 10:53 PM.
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