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Root Questions about undervolting

jackdubl

jackdubl

Android Expert
Am now running my first custom rom, bamf 1.8.6. I have it overclocked but don't know how to undervolt. The is a governor in the cup settings- does that have anything to do with undervolting or does this just affect the processor speed? Also, what is the range for undervolting, ie, how low can you go?
 
jackdubl said:
Am now running my first custom rom, bamf 1.8.6. I have it overclocked but don't know how to undervolt. The is a governor in the cup settings- does that have anything to do with undervolting or does this just affect the processor speed? Also, what is the range for undervolting, ie, how low can you go?
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Undervolting is a kernel thing, not a ROM thing, although a ROM with a baked in kernel that supports undervolting may have some built-in controls for it.

I am not sure what kernel is used with that ROM. If it is one of Imo's, you can do some basic undervolting using the speedtweak.sh command in the terminal. It allows you to do overclock/undervolt combos by simply selecting them from a text menu.
 
jackdubl said:
So what would the governor affect? And within what range of frequencies should one undervolt?
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The governors are algorithms that determine what speed to run your processor. I don't think they control voltages--they control clockspeed. They slow the processor down to save power when not much is going on and ramp it back up when needed.

Vipermod is one undervolting script. It sets a voltage for every enabled frequency in the kernel. It steps up or down in incremements of 25 mV. It does either across the board voltage changes for all frequencies or you can tinker with each clock speed individually. Vipermod is developed in close coordination with Tiamat--an AOSP only kernel.

I am not sure what speedtweak does with voltages. It does undervolt--either mildly or a lot. It does not explicitly say what it does.
 
Haven't read up on this, I ususally just use the speedtweak.sh script for my overclock/undervolt needs but you can also look into IncrediControl it looks to me to be something like setCPU but for use with undervolting. I would think you could make your system unstable with the app or fooling around with undervolting in general so I would recommend small steps at a time. Remember this will not work with every kernel so you would need to either make sure the kernel has the requirements or test it out and see if it works.

http://forum.xda-developers.com/showthread.php?t=1192271 XDA link for the thread about this as well
 
Yeahha said:
Haven't read up on this, I ususally just use the speedtweak.sh script for my overclock/undervolt needs but you can also look into IncrediControl it looks to me to be something like setCPU but for use with undervolting. I would think you could make your system unstable with the app or fooling around with undervolting in general so I would recommend small steps at a time. Remember this will not work with every kernel so you would need to either make sure the kernel has the requirements or test it out and see if it works.

[MOD] IncrediControl v1.0! - Easy GUI Undervolting - xda-developers XDA link for the thread about this as well
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Maybe I'm just not running the script correctly. I open terminal emulator(Starts with a "$"), I enter "su"(get "#"), I enter "speedtweak.sh"(get "Speedtweak.sh not found").
 
What kernel are you using? It has to either be equipped with the speedtweak.sh script stock or you have to flash the mod
 
Yeahha said:
What kernel are you using? It has to either be equipped with the speedtweak.sh script stock or you have to flash the mod
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Running the kernel that came with the bamf 1.8.6 rom. It said it supported undervolting, at least under the first release.
 
It looks like the stock kernel for your rom bases it's voltage on where the cpu is clocked at. Upon flash it is volted at stock and clocked at 1.19 if you clock it at or below 1.00 then it will be undervolted, if you clock it above 1.19 then you will be overvolted.

If you want the speedtweak.sh script to work, read up here [Mod] ScriptFusion - Any Kernel {7/29/11 - 1:00 AM EST} - xda-developers and follow the direction, or just flash a kernel with it already cooked into it (easiest thing to do ;))
 
Having been using script fusion for a little while now, it is kernel sensitive despite being billed as any kernel compatible. Its also VERY detailed, I'd go with Imosyons kernel and just use the voltage settings in init.d once the speedtweak script is run in terminal emulator.
 
Yeahha said:
It looks like the stock kernel for your rom bases it's voltage on where the cpu is clocked at. Upon flash it is volted at stock and clocked at 1.19 if you clock it at or below 1.00 then it will be undervolted, if you clock it above 1.19 then you will be overvolted.
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So it's already tweaked to be undervolted? Should I just keep it or use Imosyon?
 
When i use bamf i usually keep the default kernel, but if your unhappy with performance or battery life try a new one
 
jackdubl said:
So it's already tweaked to be undervolted? Should I just keep it or use Imosyon?
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Are you having issues with the stock kernel? Fast battery drain, issues with lag, wake issues... If so then I would try a different kernel, I'm sure in the thread for the rom there are many suggestions for different kernels
 
Yeahha said:
Are you having issues with the stock kernel? Fast battery drain, issues with lag, wake issues... If so then I would try a different kernel, I'm sure in the thread for the rom there are many suggestions for different kernels
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No problems whatsoever. In fact, it's like having a vastly improved phone in all respects. All my hidden "videos" thumbnails now load instantly whereas on stock I have to adjust the screen orientation to get them to all load. Too many improvements to list. May just run this until official GB roms start coming out. Of course, I say that now...
 
That is what nandroid is for, you can back up flash something else and try it out, if you like your set up before restore the nandroid and it is just like your phone was before you flashed the other rom.
 
So I've just used Speedtweak and set it to batterysaver. Does vipermod allow me to further undervolt and has it noticeably help battery life for anyone?
 
OK based on some more research and this post: xda-developers - View Single Post - [ROM][TH3ORYROM] A05PTH3ORY V1.4X [AOSP/CM7] DKSM Kernel (8/14/2011) I've got an idea of where to start for undervolting.

Many roms are now including both Speedtweak.sh and Vipermod but these are redundant and override each other when it comes to changing voltages. If you choose batterysaver in Speedtweak and then in Vipermod lower all the voltages by 100mv then you override the Speedtweak voltages, you do not lower the Speedtweak settings by another 100mv. If you do not want to bother with stress testing via Quadrant as suggested in the XDA post it seems like many users are only using Vipermod to lower voltages by 100mv. The end result are voltages that are 75mv-100mv lower then the battersaver setting in Speedtweak.

EDIT: did more playing around and Vipermod and speedtweak.sh do affect each other i now believe. I'll try to investigate more, but just thought I should update this.

Now to convince you why you should undervolt: Using Current Widget I can now see that when my TB is idling/screen off the current draw is 18-26mA whereas before I would be 38-42mA if I was lucky. I definitely suggest trying it out, takes only a few seconds to boot up Vipermod and lower the voltages
 
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