Discussion: Undervolting Intel CPUs with unRAID


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  • 1 month later...

I used to do this on my Old G1 T-Mobile Android phone when it first came out. Advantages was I was able to seriously stretch the battery life of my phone and when applications needed the CPU it would ramp back up to normal.  Have zero clue how the coding exactly worked, but it worked well. 

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  • 2 years later...

Thread gravedigging...

 

Managed to get into an interface of some sort using CLI and python3 for undervolting. I haven't tested it yet though.

 

I used this python script, pulled it with git (pip3 did not work for me) and then ran it with python3.

https://github.com/georgewhewell/undervolt

root@sorrentoshare:~/undervolt# python3 undervolt.py --read
temperature target: -0 (100C)
core: 0.0 mV
gpu: 0.0 mV
cache: 0.0 mV
uncore: 0.0 mV
analogio: 0.0 mV
powerlimit: 105.0W (short: 0.00244140625s - enabled) / 84.0W (long: 8.0s - enabled)

 

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  • 3 weeks later...

Another grave-dig:

 

I haven't done any consistent temperature or AIDA 64 testing - that will come in a couple of months after work and holidays calm down, but, I have a -100mV undervolt set just to see what happens. No crashes so far. It appears that there is an overall temperature reduction of 2C, but it is hard to tell.

 

So, further testing for later:

  1. Boot unraid with all dockers stopped, find an aida64 tester docker
  2. Benchmark with a stable ambient temperature and 0mV offset.
  3. Begin applying offsets in BIOS (if possible, haven't checked), if not, back to intel-undervolt
  4. Re-apply benchmark test, rinse and repeat until instability in AIDA 64

I'd also like to test idle power, specifically if this type of undervolting will interfere with any automatic power stepping in the Haswell CPUs (I'm running a 4770).

 

This is an interesting script, because with user scripts you could in theory apply your own power stepping (say reset offsets to zero when spinning up a VM and then reduce them when the server is unloaded). From what I have read changing offsets disables intel power states, but I am not sure if that happens with this script too.

 

temperature target: -0 (100C)
core: -99.61 mV
gpu: -75.2 mV
cache: -99.61 mV
uncore: -99.61 mV
analogio: -99.61 mV
powerlimit: 105.0W (short: 0.00244140625s - enabled) / 84.0W (long: 8.0s - enabled)

 

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  • 3 months later...

I tried this out, too.

 

At first I installed undervolt from here:

https://slackware.pkgs.org/current/slackware-x86_64/undervolt-20200612_07d0c70-x86_64-1.txz.html

 

In addition I installed "python3-3.8.2-x86_64-1.txz" through the NerdPack Plugin. After that I was able to execute the read command:

undervolt --read
temperature target: -0 (100C)
core: 0.0 mV
gpu: 0.0 mV
cache: 0.0 mV
uncore: 0.0 mV
analogio: 0.0 mV
powerlimit: 65.0W (short: 8.0s - enabled) / 4090.0W (long: 8.0s - enabled)

Then I set -100mV and it seemed to work:

undervolt --core -100 --cache -100

undervolt --read
temperature target: -0 (100C)
core: -99.61 mV
gpu: 0.0 mV
cache: -99.61 mV
uncore: 0.0 mV
analogio: 0.0 mV
powerlimit: 65.0W (short: 8.0s - enabled) / 4090.0W (long: 8.0s - enabled)

And now the result in idle:

Before: 24.39W

After: 23.88W

Reduction: ~0.50W

 

Its not much, but a nice addon to the good results of the powertop tweaks. And of course undervolting reduces power consumption on high loads as well. Maybe I find a method to compare high load consumption as well.

 

As I do not know how far an i3-8100 could be undervolted I leave this setting until I find out more. 

 

P.S. I tested this command as well, but there was no difference in idle:

undervolt --gpu -75 --core -100 --cache -100 --uncore -100 --analogio -100

undervolt --read
temperature target: -0 (100C)
core: -99.61 mV
gpu: -75.2 mV
cache: -99.61 mV
uncore: -99.61 mV
analogio: -99.61 mV
powerlimit: 65.0W (short: 8.0s - enabled) / 4090.0W (long: 8.0s - enabled)

 

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  • 11 months later...

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