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pernix

Member

Registered: 2011-09-13

Posts: 7

Setting up the correct voltages for PHC

Hi all!
I'm trying to use PHC to undervoltage my cpu, but I can't find how to set the correct voltages.
I installed phc-intel from AUR and /sys/devices/system/cpu/cpu0/cpufreq/phc_controls file contains the following line:

33:0 22:0 20:0 19:0 18:0 17:0 16:0 15:0 14:0 13:0 12:0 11:0 10:0 9:0 8:0

While in /etc/conf.d/phc-intel there's:

# voltage IDs to be set for all CPUs
VIDS=""

I read the wiki page about PHC, but I found only this:

[...]After the phc module is compiled and the lowest voltages are found[...]

and it's not really helpful...
Can anyone help me?
My CPU is an Intel i2720 processor.

Thanks a lot!

pogeymanz

Member

Registered: 2008-03-11

Posts: 1,020

Re: Setting up the correct voltages for PHC

There is a script in the AUR called linux-phc-optimize that will gradually decrease your voltage until it finds the sweet spots. Make sure you aren't working on anything important when you run it.

pernix

Member

Registered: 2011-09-13

Posts: 7

Re: Setting up the correct voltages for PHC

There is a script in the AUR called linux-phc-optimize that will gradually decrease your voltage until it finds the sweet spots. Make sure you aren't working on anything important when you run it.

I've ssen it, but it links to a non existent file (http://www.s3pp.de/misc/linux-phc-optimize.bash) and the compilation fails...

EDIT: I'll use the intel-phc-undervolt.bash file to see if it works.

Last edited by pernix (2011-09-13 17:34:10)

pernix

Member

Registered: 2011-09-13

Posts: 7

Re: Setting up the correct voltages for PHC

I'll use the intel-phc-undervolt.bash file to see if it works.

It seems that it's quite useless: it determines the lowest available voltage, but starting from 0 it sets 0 for each FID. The question is: how can the voltage be zero???

pogeymanz

Member

Registered: 2008-03-11

Posts: 1,020

Re: Setting up the correct voltages for PHC

I'll use the intel-phc-undervolt.bash file to see if it works.

It seems that it's quite useless: it determines the lowest available voltage, but starting from 0 it sets 0 for each FID. The question is: how can the voltage be zero???

It isn't. I remember reading about this on the ubuntuforums thread about it a few years ago. Basically, if it let's you go to 0, it means that the hardware wont accept values below its actual minimum. So it's okay for you to set your FIDs to 0 because your hardware will just go to its minimum.

pernix

Member

Registered: 2011-09-13

Posts: 7

Re: Setting up the correct voltages for PHC

It isn't. I remember reading about this on the ubuntuforums thread about it a few years ago. Basically, if it let's you go to 0, it means that the hardware wont accept values below its actual minimum. So it's okay for you to set your FIDs to 0 because your hardware will just go to its minimum.

Well, in this case I'm afraid that there's no way to decrease my cpu temperature as this program don't do anything: my idle cpu temperature is 60-62°C while with other distributions was 54-56°C (governor: ondemand; cpufreqd installed).

pogeymanz

Member

Registered: 2008-03-11

Posts: 1,020

Re: Setting up the correct voltages for PHC

I see.

What kernel version were you running in those other distros?

If you are using an intel Core iX processor, see this: http://www.phoronix.com/scan.php?page=a … ower&num=1

pernix

Member

Registered: 2011-09-13

Posts: 7

Re: Setting up the correct voltages for PHC

What kernel version were you running in those other distros?

openSUSE - kernel 2.6.37

If you are using an intel Core iX processor, see this: http://www.phoronix.com/scan.php?page=a … ower&num=1

I'll take a look at this.

EDIT: So it's a kernel related problem, am I right?

Last edited by pernix (2011-09-13 22:31:09)

pernix

Member

Registered: 2011-09-13

Posts: 7

Re: Setting up the correct voltages for PHC

Ok, I've followed these instructions, and now my temperature is 5°C lower.