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Discussion Starter · #1 ·


Why Undervolt

Processors work at a certain voltage. There is also electrical current flowing into the CPU can work. When a CPU works, it uses power and produces heat. More heat means higher temperature of the CPU and more heat for the notebook. When CPU is under load it heats faster since it draws more power.

For this guide I am using an Intel mobile processor which has a technology called Speedstep. It enables a CPU to use different power levels depending on the load. It is somewhat like AMD's Cool n' Quiet technology. The higher the load in the CPU, the faster it works, and the more heat that it puts out. It does it in steps. When on idle it uses the lowest multiplier, when under 100% load it uses the highest multiplier. It can sense and switch steps every 1/2000 of a sec.

Multipliers

Every multiplier works at a different voltage. The lower the multiplier, the lower the voltage thus lower the heat produced. The lowest multiplier is 6x on T7500. The highest is 11x and it uses 1.300v stock. 11x and other multipliers are open for the voltage change. Also note that other processors can have even higher multipliers.

The Basic Concept

If you lower the voltage per every mulitiplier then the processor should be cooler no matter what the multiplier being used is since it is using less power than it would have stock.

How low is too low

This is an important question since the stability of the CPU drops along with the voltage. That is why we stress test the CPU after every change that we make with programs such as Orthos, Prime 95 and other programs. Even 3D Mark can show some of instabilities. For this guide I have tested the shown voltages in Orthos and games and have found no instabilities. But I have seen the significant temperature drop in games â€" over 15 degrees C. It is important to mention that the SPEED of the CPU stays the SAME! It is cooler, not slower. Undervolting is giving you the same speed but at lower temperatures.

Tools Needed

RM Clock Utility 2.35
Orthos

The Processor that will be used for this is the Intel® Core™2 Duo Mobile Processor T7500.

CPU Speed: 2.2 GHz
PCG: 11
Bus Speed: 800 MHz
Bus/Core Ratio: 11
L2 Cache Size: 4 MB
L2 Cache Speed: 2.2 GHz
Manufacturing Technology: 65nm
Core Stepping: G0
Thermal Design Power: 35w
Thermal Specification: 100*c
VID Voltage Range: 1.03 - 1.30v

This is a screen shot of the original voltage that the Intel T7500 uses for each multiplier 6x - 11x.


This is a screen shot of the voltages that I have successfully reached for each multiplier 6x - 11x. These are voltages that I have played with with by lowering the voltage slightly then testing. These are not the lowest I can go but at these voltages I have 100% stability which is key. To change a voltage pick the multiplier that you want to change and lower it a setting, then run orthos for at least 15 minutes.


This is a great built in monitering tool that is built into RM Clock. It shows temperature, clock speeds, voltages, CPU loads, and the multiplier.


This is the profiles page, where up top you want it to always say power on demand so that it allows the processor to throttle and not stay at a certain multiplier. You can set it to Maximum Performance mode but it will cause the CPU to stay at full speed and keep the idle temps quite high.


This is the settings page where you can make changes to RM Clock. Also once you are happy with some new stable voltages. Make sure that you click start on setup.


This is a screenshot showing my idle temperature with a multiplier of 8 at 1.000v. My idle actually gets lower as my idle voltage is 0.850 not 1.000. I actually truely idle around 34*c.


This is a screenshot of stock volts after only a few minutes of Orthos. Look at my temperature! Im already at 74.2*c!


This is a screenshot showing me running Orthos with my new voltages of 1.125 down from 1.300. Temp was maxed at around 63* after over 17 minutes!


Conclusion

Overall with a little time and patience. You can lower the temps of your CPU in your notebook, therefore lowering the temps of other components in the notebook and increasing the life of the CPU. This is really a safe process and in no way will affect performance at all! Just remember to go slow and take your time!
 

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Handy reference! Please note that the IDA and SuperLFM modes are only available on Santa Rosa-based machines (2nd Gen Merom and Penryn). The rest of us have less to use.

I'm surprised you actually increased the voltage on the lower multipliers from the stock settings. If I were you, I'd bounce 6-8x back to the stock setting.
 

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I did underclock my system for a while when I was running XP, but despite running ORTHOS without any problems, it had random freezes. So I went back to stock, and now that I'm on Vista, I don't want to deal with the issues RMClock has with it.
 

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Discussion Starter · #7 ·
Quote:

Originally Posted by rcf22 View Post
Very useful guide. This will be great to keep lappys cooler and save battery life!
Thanks! Yea I have yet to have any problems so far and RM Clock hasnt given me any issues so far. It loads and runs properly every time.
 

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Discussion Starter · #9 ·
Quote:

Originally Posted by hermit View Post
quick question (and possibly dumb). where do you undervolt the cpu? is it in RM Clock Utility 2.35 itself? because i can't get to the bios on my laptop, at least not by the usual method i use on my main rig (hitting DEL until something happen).

thanks
Yea its in the program itself. It allows you to change the voltage per multiplier. Any questions feel free to ask!
 

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Discussion Starter · #13 ·
The idle should be the same as I dont believe that you can change the voltage for the lowest multiplier. However loads should drop noticibly. I saw roughly a 10* drop on load.
 

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well, it looks like it run correctly, and i have the exact same temps as you. stable for 30 minutes

oh well, at least, battery life should be a bit better

my cpu is a t7700 on an Asus G1S
 

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Discussion Starter · #15 ·
Thats a nice CPU! Yea battery life should increase and as long as your stable all is good. You might want to run Orthos for a good testing. I only ran in for a short amount of time in my tutorial just to show temps but not to actually test stability. However I have run Orthos for 8 hours and was fine.
 

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Discussion Starter · #17 ·
Quote:

Originally Posted by Fox_Smash View Post
this seems very nice,will try it on my notebook later(sempron 3500+).
I have actually done a little more testing and got my max volts down to 1.875 totally stable. I will update the guide soon. If you have any questions let me know
 

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This dont work on a Celeron M 530? Is it because it dont have speedstep? is there any other way to undervolt a celeron? My batterytime is really bad, like 1 hour..
 

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Discussion Starter · #19 ·
huh im not sure why it didnt work. Speedstep shouldnt effect is as your only really lowering the voltage of the highest multi so that when the CPU runs at full power its not getting full volts thereby lowering temps.
 

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Quote:
Processors work at a certain voltage. There is also electrical current flowing into the CPU can work.
Processors work at a certain range of voltages. Undervolting has nothing to do with current. It has to do with reducing signalling voltaage which in turn reduces power.
 
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