Undervolting @ 2009

TigTex · 2009-10-18 23:03:23

The undervolting business is interesting.

On windows I can get almost 20% more battery time and less heat from my laptop.

The problem is that there is no updated way to do this. Every package is old and also the PHC wiki isn't complete. Searching the foruns gives me outdated solutions

I'm using a core 2 duo 2.53ghz (T9400) cpu. With acpi-cpufreq my system throttles down without any problem, but it uses "stable" voltages defined by intel. For example, at full speed I have 1.165v and I have my pc 100% stable with 1.050v @ windows. It's a huge improvement.

So... I really would love to do this on arch linux. THis is the only thing that I can do on windows but I can't do it here.

Using phctool it doesn't show me any VID in this cpu.

Anyone had sucess with this?

Thanks and let's reduce our heat production

Last edited by TigTex (2009-10-18 23:11:07)

wankel · 2009-10-19 05:22:06

I have successfully done this on my laptop (dell vostro 1400 with core2duo).

Install phc-intel from the aur. and then reboot. Type the following:

cat /sys/devices/system/cpu/cpu0/cpufreq/phc_controls

And you should have something like:

9:45 8:30 6:20 136:15

Your numbers will vary of course.

Next, take the smallest number and use that for all of them. So in my case:

9:15 8:15 6:15 136:15

Next, add the following command to your /etc/rc.local file

echo "12:21 10:1 8:1 6:1" > /sys/devices/system/cpu/cpu0/cpufreq/phc_controls

That should take care of both cpu0 and cpu1. Reboot and type in the first command to see if the new values were set.

gog · 2009-10-19 06:09:26

http://wiki.archlinux.org/index.php/PHC

TigTex · 2009-10-19 07:47:51

Hummm, I did read the wiki but I found that the problem was with phctool.

[root@tigtex-pc tigtex]# cat /sys/devices/system/cpu/cpu0/cpufreq/phc_controls
10:43 73:37 6:23 134:19

I indeed have something here. But doesn't seems to be working and frequency ID's are strange...

[root@tigtex-pc tigtex]# echo "10:23 73:19 6:19 134:19" /sys/devices/system/cpu/cpu1/cpufreq/phc_controls 
10:23 73:19 6:19 134:19 /sys/devices/system/cpu/cpu1/cpufreq/phc_controls
[root@tigtex-pc tigtex]# echo "10:23 73:19 6:19 134:19" /sys/devices/system/cpu/cpu0/cpufreq/phc_controls 
10:23 73:19 6:19 134:19 /sys/devices/system/cpu/cpu0/cpufreq/phc_controls
[root@tigtex-pc tigtex]# cat /sys/devices/system/cpu/cpu0/cpufreq/phc_controls 
10:43 73:37 6:23 134:19 
[root@tigtex-pc tigtex]# cat /sys/devices/system/cpu/cpu1/cpufreq/phc_controls 
10:43 73:37 6:23 134:19

Nothing happens....

My cpu has from 6x to 9.5x multiplier and a SuperLFM mode (@ 6x)

Last edited by TigTex (2009-10-19 07:56:44)

wankel · 2009-10-19 17:43:52

This might have nothing to do with it, but could it be because youre missing the ">" before "/sys/devices......"?

ammon · 2009-10-19 19:07:53

Can cpu be undervolted ondemand?

ngoonee · 2009-10-19 23:25:08

Yes, if you have the PHC module. Though you actually set the undervolting based on the CPU freq scaling, so once you have it set properly there's no reason to change it I believe. If its stable, any extra voltage is useless, doesn't give more performance.

ammon · 2009-10-20 15:34:49

Ty ngoone, but I need further help.

This is what I got:

cat /sys/devices/system/cpu/cpu0/cpufreq/phc_controls 
11:45 10:37 8:28 6:18 136:11

What does ti mean? I have T7250, http://processorfinder.intel.com/detail … Spec=SLA49
Proc specs say it is made to run at 1.075V-1.175V, do nubers from cat .... mean something about voltage? Or multipliers?
What number am I looking for? Wankel mentioned that I need smallest number. That is 8:26? And what to do with it?

P.S.
I have installed phctool, now I have gui, to see what am I doing. I have 5 steps, from 1.275V to 0.85V, according to freq step.
Does it mean proc uses 0.85V for lowest freq (800Mhz)? If that is true, than should I change it? And by how much can I change voltage without risking cpu freeze, damage...

Last edited by ammon (2009-10-20 15:44:39)

TigTex · 2009-10-20 15:46:52

wankel wrote:

This might have nothing to do with it, but could it be because youre missing the ">" before "/sys/devices......"?

OMG!.................................................

I can't believe I forgot the ">"...... OMG!!!!!!

In deed it works, my system crashed with 2.53ghz because voltage was too low
I also have the same doubt as ammon.

there is no correlation between 134:19 and 6x (superLFM)@ 0.95v....

Last edited by TigTex (2009-10-20 15:47:44)

buddabrod · 2009-10-20 16:48:45

ammon wrote:

P.S.
I have installed phctool, now I have gui, to see what am I doing. I have 5 steps, from 1.275V to 0.85V, according to freq step.
Does it mean proc uses 0.85V for lowest freq (800Mhz)? If that is true, than should I change it? And by how much can I change voltage without risking cpu freeze, damage...

Yes,the lovest voltage is used by the lowest frequency. However the lowest voltage cant be changed for the newer intel cpus, only the others.

You cant really harm you cpu by lowering the voltage, you can just corrupt your filesystem

Just reduce it by a little, do stress testing and then lower again.. I took the voltage where my system crashed and increased it by 3 steps to have assured stabillity. And it works. On my T7500 I have about 10°C lower core temperature..

wankel · 2009-10-20 19:33:14

ammon wrote:

Ty ngoone, but I need further help.
This is what I got:
cat /sys/devices/system/cpu/cpu0/cpufreq/phc_controls 
11:45 10:37 8:28 6:18 136:11

For instance, this would have been 11:11 10:11 8:11 6:11 136:11. The first one might be a little low, so you can give this a shot and tweak it a bit if the systems crashing.

This is a massive thread, but it should answer your questions if you havent been through it already:
http://ubuntuforums.org/showthread.php?t=786402

ammon · 2009-10-22 17:01:57

Ty wankel

@buddabrod
Can you lower voltage on lowest freq? It seem I can, on T7250.

So far so good, I reduce voltage, lock proc on freq I test and run makepkg on kernel.

Last edited by ammon (2009-10-23 13:22:17)

buddabrod · 2009-10-23 09:25:42

ammon wrote:

Ty wankel
@buddabrod
Can you lower voltage on lowest freq? It seem I can, on T7250.
So far so good, I reduce kernel, lock proc on freq I test and run makepkg on kernel.

You can change the values, but it doesnt affect anything.Some intel guy wrote this on the power mailinglist. So as I said you can just change the voltages for the other frequencies, but not for the lowest.

ammon · 2009-10-23 13:25:02

I have noticed fs is corupted after testing. But system did not crash. How to know if voltage is enough to keep system and fs stable?

Arch Linux

#1 2009-10-18 23:03:23

Undervolting @ 2009

#2 2009-10-19 05:22:06

Re: Undervolting @ 2009

#3 2009-10-19 06:09:26

Re: Undervolting @ 2009

#4 2009-10-19 07:47:51

Re: Undervolting @ 2009

#5 2009-10-19 17:43:52

Re: Undervolting @ 2009

#6 2009-10-19 19:07:53

Re: Undervolting @ 2009

#7 2009-10-19 23:25:08

Re: Undervolting @ 2009

#8 2009-10-20 15:34:49

Re: Undervolting @ 2009

#9 2009-10-20 15:46:52

Re: Undervolting @ 2009

#10 2009-10-20 16:48:45

Re: Undervolting @ 2009

#11 2009-10-20 19:33:14

Re: Undervolting @ 2009

#12 2009-10-22 17:01:57

Re: Undervolting @ 2009

#13 2009-10-23 09:25:42

Re: Undervolting @ 2009

#14 2009-10-23 13:25:02

Re: Undervolting @ 2009

Board footer