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Root A question about undervolting...

corybantic

corybantic

Well-Known Member
I'm running Myn's Warm 2.2 RLS 5 with netarchy-toastmod 4.3.4-cfs-havs-more sbc kernel. Along with the Overclock Widget, I've been able to easily get over 17+ hrs with very moderate use out of my Evo. My question is regarding undervolting. I've done some research and have 3 questions: undervolting is done via a new kernel which would mean I would have to discard my existing kernel, correct? For Sense based Roms, what would be a good undervolting kernel? Why would anyone want to Overvolt? Thanks!
 
So the kernel you have is perfectly ok to undervolt. When I was on sense I used that kernel to undervolt to 128 without any issues. As far as overclocking goes people do it to make your phone a little more snappy and quick.
 
corybantic said:
I'm running Myn's Warm 2.2 RLS 5 with netarchy-toastmod 4.3.4-cfs-havs-more sbc kernel. Along with the Overclock Widget, I've been able to easily get over 17+ hrs with very moderate use out of my Evo. My question is regarding undervolting. I've done some research and have 3 questions: undervolting is done via a new kernel which would mean I would have to discard my existing kernel, correct? For Sense based Roms, what would be a good undervolting kernel? Why would anyone want to Overvolt? Thanks!
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I use myn 2.2 with netarchy-toastmod 4.3.4-cfs-havs-more sbc kernel. (along with cm7 depending on the day).

to answer your answer questions:
1- I believe you can undervolt the kernel you already have. I have mine set to 128min with setcpu, with screen off. Dont think you need a new kernel for undervolting. Just use the one you have with setcpu.

2- netarchy-toastmod 4.3.4-cfs-havs-more sbc kernel.... :)

3- Overvolting will give your phone higher clock speed, and possiblity make your phone run somewhat smoother when working with larger applications/games...etc
 
Guys, clock speed and voltage are *not* the same thing. Over/underclocking is the process of changing your min/max CPU clock frequency. It basically makes things run faster or slower (that was an over-simplification :p). Over/undervolting is when you either supply more or less voltage to the CPU. It has no affect on the clock speed, and does not make things run faster or slower. It impacts stability, only. If you undervolt, you have the potential to save battery life, but you could make the phone unstable. If you underclock, you have the potential to save battery life, but could make the phone slow. If you over-volt, you could make the phone more stable, but waste battery. If you overclock, you could make the phone faster, but waste battery. They are not the same, and do not necessarily rely on each other. Of course, higher frequencies require higher voltages. You can either supply a static under-volt, or go with HAVS, which will user lower voltages when the frequency is low, and raise them up at the frequency goes up. Generally speaking, the highest supplied voltage will be as low as possible to maintain stability at a given frequency. That being the case, unless you have stability issues, HAVS is your best bet if you want to under-volt. Since you already have it, you're good. I believe netarchy also has a static under-volt kernel, as well, which will under-volt more than usual, but it will not change based on the frequency.

All that being said, I'm sure you may have heard that you've heard that you shouldn't use setcpu profiles if you're using HAVS. Some people may have seen some weird behavior, but it's likely not due to this. Setcpu profiles affect the frequency. HAVS affects the voltage, which is completely automatic, and will work at whatever frequency you have set.
 
akazabam said:
Guys, clock speed and voltage are *not* the same thing. Over/underclocking is the process of changing your min/max CPU clock frequency. It basically makes things run faster or slower (that was an over-simplification :p). Over/undervolting is when you either supply more or less voltage to the CPU. It has no affect on the clock speed, and does not make things run faster or slower. It impacts stability, only. If you undervolt, you have the potential to save battery life, but you could make the phone unstable. If you underclock, you have the potential to save battery life, but could make the phone slow. If you over-volt, you could make the phone more stable, but waste battery. If you overclock, you could make the phone faster, but waste battery. They are not the same, and do not necessarily rely on each other. Of course, higher frequencies require higher voltages. You can either supply a static under-volt, or go with HAVS, which will user lower voltages when the frequency is low, and raise them up at the frequency goes up. Generally speaking, the highest supplied voltage will be as low as possible to maintain stability at a given frequency. That being the case, unless you have stability issues, HAVS is your best bet if you want to under-volt. Since you already have it, you're good. I believe netarchy also has a static under-volt kernel, as well, which will under-volt more than usual, but it will not change based on the frequency.

All that being said, I'm sure you may have heard that you've heard that you shouldn't use setcpu profiles if you're using HAVS. Some people may have seen some weird behavior, but it's likely not due to this. Setcpu profiles affect the frequency. HAVS affects the voltage, which is completely automatic, and will work at whatever frequency you have set.
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thanks for the clarification...yeah for some reason I read undervolt and overvolt....but my brain translated it to under and over CLOCK!...ugh

I need more coffee!
 
Haha, no worries. I think we've all done that before. I just wanted to make sure there is no confusion about the difference.
 
So if you already have a kernel with HAVS, is it pointless to run an undervolt script? I know Viper has some that work with Tiamat and I assume some other AOSP kernels, but I've never messed around with it. How does an undervolt script affect a kernel that already has HAVS? Does it just lower the base that HAVS would normally go off of? Or is an undervolt script only effective in a situation where the voltage is constant?

I've thought about flashing an undervolt script but I don't really know all the specifics. I figure akazabam would know.
 
MizzouBrent said:
So if you already have a kernel with HAVS, is it pointless to run an undervolt script? I know Viper has some that work with Tiamat and I assume some other AOSP kernels, but I've never messed around with it. How does an undervolt script affect a kernel that already has HAVS? Does it just lower the base that HAVS would normally go off of? Or is an undervolt script only effective in a situation where the voltage is constant?

I've thought about flashing an undervolt script but I don't really know all the specifics. I figure akazabam would know.
Click to expand...

Those scripts are specifically designed to work *with* HAVS. Basically, there is a file in /sys that defines the different voltage levels for each frequency. When the CPU is running at a certain frequency, it will then know which voltage to use. These undervolt scripts work with kernels that have been modified to allow such changes. The script is a startup script (runs from init.d) that will modify this file with a specific negative number. This number is the number to undervolt even further at each voltage level. You basically have to try different ones, starting with the most conservative, and work your way up until it's unstable, then go back one. Another method is to start with the least conservative (knowing it will probably be unstable) and work you way down until it's stable.
 
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