Can you undervolt a desktop?

llmercll

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Nov 20, 2008
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I was wondering if this is possible, or recommended. I use it on all my notebooks and achieve wonderful temp decreases.

I've got it at standard clocks right now, and don't plan on overclocking until I feel I need it. (and as such, I'm using stock cooling)

thank you!
 
Yes it is and in fact several users here undervolt their PC's to try to have a better impact from an environmental sustainability perspective.

Let us know what mobo and cpu you have and I am sure there is someone here who can give you some advice.

Cheers.

 


Its only possible if his M/B allows that option.
 
True ... hence I wanted to know what the mobo and cpu combo was.

Otherwise my generic post stands as it is.

Reduce (power use)
Reuse (Systems)
Recycle (Systems)
Integrate (Decision Making)
Involve (Others)
Caution (with dangerous decisions that may impact on the environment)
Generational Equity (Leave the place in good order for the kids)
Ecological Integrity
Continuous Improvement

Hope this helps ... I teach it.
 
To the OP, if your M/B will allow manipulating your CPUs Vcore voltage, I strongly recommend going no lower than the lowest voltage your CPU is spec'd to run at, if you do not give that CPU its minimum voltage, its not going to run properly and may not even post at all.
 
OP since AMD make a number of AM3 processors including a few low power units, the core voltage on your mobo will be able to dial down a few notches ... to take into account these being fitted.

By default the core voltage for your 720 is 1.325 ... check how this overclocking chart shows voltage being increased as the frequency is increased (in order to stabilise the cpu). Albeit this one is a black (unlocked).

http://www.cluboc.net/reviews/cpu/amd/X3_720_X4_810/p2.asp

You should be able to decrease the core voltage in small steps until the system becomes unstable ... then simply go back to the last voltage with a good result.

There should be a corresponding drop in the power envelope, since P=E.I

Since there are a few (cherry picked) low voltage, and mobile parts, there is no reason why you can't shave a few watts off your system ... you might not get a lot ... but the fun is in trying.

Your mobo manual is here:

http://asia.giga-byte.com/FileList/Manual/mb_manual_ga-ma790gpt-ud3h_e.pdf

Keep us posted on how you go and good luck.

Here is a breakdown on the other AM3 cpu's for reference:

http://products.amd.com/en-us/desktopcpuresult.aspx?f1=&f2=&f3=&f4=&f5=&f6=&f7=45nm+SOI&f8=&f9=&f10=&f11=&f12=True
 

loneninja

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I still havn't gotten time to find the minimum stable voltage on my Phenom II or Athlon II, but my Phenom 9850 @2.5 is stable with 1.125V while it's stock voltage is 1.3V. Made a big difference in heat, so I would assume the same for power consumption.

I'm a big fan of both underclocking/undervolting and overclocking. No reason to run an overclocked machine 24/7, its only for when I'm doing something cpu intense like rendering in 3ds max.
 



Actually the stock 9850s voltage is 1.05-1.30V, according to AMDs website.
 

llmercll

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OK this is bad. I undervolted waaay to much and now my system wont post...

I set it to -.300 voltage, assuming it might be able to go that low, and if it couldn't, would at least reset to defaults after failing. but it hasn't...and i cant post.

Anyone know what I can do to fix this? Some way to reset my BIOS?
 


Ooops :D

What is neat about the Gigabyte is you can save 10 different BIOS configurations and profiles for different CPU overclocks/undervolts. Makes it easier when you have to reset ..... alot.

You can pop out the battery, hit the power switch and wait a minute or so if you don't want to play with the jumper.
 

llmercll

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Woohoo, tried it again with -.100 voltage and working well so far. Though it didn't actually undervolt .100, it undervolted .200. In reality it went from 1.36 to 1.18 (according to cpu-z)

So .300 was really .600. No wonder it wouldn't post. My cpu was running at about .6v max load. probably .3 or .4 at idle clocks LOL

Big big big temp decreases. Down from 65c to 47c under load, and from 37c to 29c on idle. Really good stuff guys.
 

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