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Discussion: Undervolting Intel CPUs with unRAID

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well you'd decrease power consumption as well as heat, both are worthy reasons.
For a 24/7 appliance that can be a deal breaker for some (i'm openly wasteful lol)

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Just curious. How much energy savings would this provide for a typical user?

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8 minutes ago, bjp999 said:

Just curious. How much energy savings would this provide for a typical user?

 

Curious myself, current Intel CPUs already use so little power at idle, does undervolting also help at full load?

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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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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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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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