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Undervolting FAQ

I read a lot about undervolting on here and i think i have an idea about what it does but i may be way off, and im sure each device is different. in pimp my cpu there are multiple options, and while this sounds newbish i think this should be explained to folks in some more detail.
this is what im assuming.
undervolting allows for less power consumption.
UV on higher OC levels controls power spikes to the CPU?
what is a safe level to UV and at what frequencies specific to the G2x
i am reading up on this, to get a better idea. http://www.android.net/forum/android-rooting/58117-droid-x-guide-undervolting-guide.html

Here's my understanding of the whole undervolting thing..
In order to maintain stable operation across devices with varying production quality (not all chips are created equal), manufactures use voltage levels higher than necessary for most devices. They cater to the least common denominator. But most phones will still operate reliably at a lower voltage. By undervolting you can extend your battery life and ward off chip killing heat. This all becomes even more important when overclocking. When you overclock your device you increase the power usages (those extra megahertz aren't without cost). This increases both the drain on your battery and the heat produced by your CPU. Undervolting helps to offset both issues.
As for the proper undervolting levels...that will vary with the tolerance of each individual device. But I'm sure someone can provide some general guidelines...sorry I haven't undervolted the g2x yet and don't want to steer you wrong.
Hope this helped...

Good info. I dropped mine .25 on each higher level. So ill see how it goes
G2x with CM7 and faux kernel

what confuses me on this topic is the "it's different for each device" phrase that I keep reading. Is this in reference to the rom/kernel that is being used or is it specific to apps installed/how the phone is used.. or is it a combo of both?
It's confusing me because its seems that OC/UV is hardware specific and each phone has the same hardware. So I don't quite get this "it's different for each device" thing..

schmit said:
It's confusing me because its seems that OC/UV is hardware specific and each phone has the same hardware.
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Each phone doesn't have the same hardware....for example, G2X has an nvidia tegra 2 and the nexus s has a hummingbird.

i think you mean this.
cybereclipse said:
Each phone doesn't have the same hardware....for example, G2X has an nvidia tegra 2 and the nexus s has a hummingbird.
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yes all g2x's have a tegra 2 chip.
But production does not always produce the same tolerances for all the chips.
ussually(with the quality control apparently given to the g2x who knows) but ussually all chips are tested and every chip that is in a g2x will perform reliably at 1ghz as it is specified and sold at.
some of these will run reliably at 1500 or better while some will not go over 1100 without starting to get unreliable.
example is the droid 1 was sold at 550 mhz. they did an update that upped it to 600mhz so they knew all chips were tested to be ok at that threshold. Mine would run at 1200 reliably no overheating(except running flash) no reboots.
with 2 different kernels. there was another kernel that they messed with the voltages so that i would get constant reboots even at 700mhz.
some droids would not run over 700 without experiencing problems.
So yes the tegra 2 chips is the same but the abilities of it can be different. they are guarenteed to run at the speed they are sold at but most will function at a much higher speed without problems while some will not.
oh just thought of a great example. the AMD tri-core processors.
those are quadcores where 1 of the cores did not pass the tests but the other 3 did so instead of scrapping the entire chip they turned off the bad processor and sold it as a tricore. there are motherboards out there that allow this core to be turned back on and many have done this and it works just fine. its just that core didnt pass whatever minimum they set on it even though it was perfectally functional they determined that if it got to this temp or didnt run at this speed(over what it was sold at) it didnt pass.
So while this kernel at this voltage may run fine on your phone it may caused reboots or lock ups on others.
hope this makes some sense.

eagle1967 said:
yes all g2x's have a tegra 2 chip.
But production does not always produce the same tolerances for all the chips.
ussually(with the quality control apparently given to the g2x who knows) but ussually all chips are tested and every chip that is in a g2x will perform reliably at 1ghz as it is specified and sold at.
some of these will run reliably at 1500 or better while some will not go over 1100 without starting to get unreliable.
example is the droid 1 was sold at 550 mhz. they did an update that upped it to 600mhz so they knew all chips were tested to be ok at that threshold. Mine would run at 1200 reliably no overheating(except running flash) no reboots.
with 2 different kernels. there was another kernel that they messed with the voltages so that i would get constant reboots even at 700mhz.
some droids would not run over 700 without experiencing problems.
So yes the tegra 2 chips is the same but the abilities of it can be different. they are guarenteed to run at the speed they are sold at but most will function at a much higher speed without problems while some will not.
oh just thought of a great example. the AMD tri-core processors.
those are quadcores where 1 of the cores did not pass the tests but the other 3 did so instead of scrapping the entire chip they turned off the bad processor and sold it as a tricore. there are motherboards out there that allow this core to be turned back on and many have done this and it works just fine. its just that core didnt pass whatever minimum they set on it even though it was perfectally functional they determined that if it got to this temp or didnt run at this speed(over what it was sold at) it didnt pass.
So while this kernel at this voltage may run fine on your phone it may caused reboots or lock ups on others.
hope this makes some sense.
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Nice...that was much better than my explanation.

cybereclipse said:
Each phone doesn't have the same hardware....for example, G2X has an nvidia tegra 2 and the nexus s has a hummingbird.
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lol. dude, I'm in the g2x forum.. not the "whatever phone ya wanna talk about" forum. I was referring to the g2x's having the same hardware, lol.
Thanks to the other guy for the awesome explanation

[Q] Can this be done? Cpu related

I read a lot of comments about the processor used by qualcomm being asymmetrical thus one core is doing the heavy lifting most of the time while the other is at a lower clock speed and it affects overall performance but enhances battery life. Now that this is a big factor on why the performance and benchmarks are lower than tegra and exynos because its running on one core most of the time.
NOW.... When we get s-off and are able to mess with the kernel, cpu speeds and such. Can there be the possibility where we can use a tool like setcpu to force both cores to run at the same clock speed always? This might level the playing field and show some drastic performance enhancements imo.
Theoretically... Is there a slightest chance something like this can be done? I suppose so since we can manipulate the cpu so easily with kernel access
Please input

nothing? lol
this might be harder than i thought...

mike21pr said:
nothing? lol
this might be harder than i thought...
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I don't think gingerbread has the capability even if the kernel was modified.

We can only wait and see

IMHO, with proper kernel, system will manage cores better and there will not be any lag. Asymmetrical core scaling will yield much better battery life then symmetrical one, just need better implementation.

[Q] Benchmarking whats really the point?

I do not understand why people make a big deal about the benchmarks for. I mean does it really prove anything? For example the HTC sensation is rocking a. 1.2 processor and the atrix only a 1 but yet the atrix will smash the sensation on a benchnark. How, so I guess I'm just wondering
A. What does a benchmark prove?
B. Shouldn't a 1.2GHZ processor be faster than a 1GHZ
I mean the atrix opens apps and scrolls faster than the sensation. How could this be and are processors just a joke?

It does not prove anything.
The most common use of benchmarks is e-penis comparison.
It can be an indicator for somewhat improvements, but that is all quite relative and subjectiv.

Then what would show processor quality?

How good a processor is should be determined by its processing power, its heat production, size and power consumption.
There is no app for that.
For testing raw processing power and getting some numbers LINPACK is okay.

Dark3n said:
How good a processor is should be determined by its processing power, its heat production, size and power consumption.
There is no app for that.
For testing raw processing power and getting some numbers LINPACK is okay.
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so 1.2 dual core or in my case 1.56 would'nt necessarily be faster at opening apps and loading pages than say a 1ghz? or is it that is has more stamina? so to speak

I am basically trying to get the answers i know people have questions to. especially more so now than ever since the development of dual core. also now that custom ROMS such as revolution HD are claiming faster processing speeds but yet there isn't an indefinite way to prove such claims. so far it seems to be up to the user and opinion.

rddocke said:
so 1.2 dual core or in my case 1.56 would'nt necessarily be faster at opening apps and loading pages than say a 1ghz? or is it that is has more stamina? so to speak
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App opening speak is not only determined by CPU clock speed.
Cpu caches, memory, system buses.
Its a whole bunch of things that determine the "speed" of a device.

In my point of view android has not been fully optimized for dual core processing, and I expect to see an improvement with icecream or what ever comes after that. Also the processors build quality, reliability and productivity is very important. As for now its just a leech sucking on the battery.

DroidFreek said:
In my point of view android has not been fully optimized for dual core processing, and I expect to see an improvement with icecream or what ever comes after that. Also the processors build quality, reliability and productivity is very important. As for now its just a leech sucking on the battery.
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Exactly what I was thinking. Long term effects are what count. Consistency is the most important it goes hand in hand with battery life.. stamina stamina stamina

[Q] What's the best way to find how overclockable your phone is?

It seems like every phone can handle a different clock speed, is there is a tried and true way to find the optimal clock speed for your phone?

No as u say every phone acts on hes own so i dont think there is any software for this ( optimal overclock) but there is software for ocing it easy like setcpu or nstools... you can oc your cpu by raising it, and using it with multitasking and if it doesnt reboot in hour or two of heavy usage then go step higher. When it reboots try with step or two higher voltages and so on until you get highest cpu with moded voltages (not more than 2 steps) stable with no reboots. Ofc i wouldnt recommend this as you are not getting anything special from it and you risk your phone... btw optimal cpu speed is its own stock speed that is just pure logic xd

Though there is no agreed upon definition, to me the optimal cpu speed is not the stock speed, the stock speed is the standard safe speed. When a CPU is manufactured it invariably has defects, the number of defects dictates the speed at which it can run. For example, when they manufacture the i5 and the i7 they probably just take defective i7 chips and turn off two cores and call it an i5. (I don't know if they actually do this with the i5 and i7 but it's been common practice with just about every processor in the past.)
I guess I should use a different term like, maximum safe speed.

Trial and error is the best way to my knowledge, haven't heard of any phone apps adjusting clocks on the fly based on temp, inaccuracies, etc, like on a computer. You can feel the temp of the phone and it'll reboot at the smallest sign of instability, just don't set test profiles to set on boot.
And what you say is correct. Processes with similar imperfections are grouped, tested and sold under a given name with the benchmark being stock frequency and voltages. Common practice and very often you get some chips you can over clock til it expands out of its bracket and others which fail at everything but stock.

[Q] Is the Infuse underclocked from the factory?

I'm running CM10, and it's running fine overclocked to 1600 MHz, yet the phone is factory clocked, (with a factory ROM), to 1200 MHz. Why? My phone seems to run perfectly fine using SmartAss2 management, but Samsung apparently purposely underclocks phones for some unknown reason. Obviously stability isn't a concern, or it would crash at 1600 MHz. Yet it is stable, so why is the default clock speed so slow? Considering the phone is perfectly stable at 1600 MHz, would it be possible to O/C my phone to 2 GHz, or would I risk frying my phone if I somehow managed to OC it by that much?

k-semler said:
I'm running CM10, and it's running fine overclocked to 1600 MHz, yet the phone is factory clocked, (with a factory ROM), to 1200 MHz. Why? My phone seems to run perfectly fine using SmartAss2 management, but Samsung apparently purposely underclocks phones for some unknown reason. Obviously stability isn't a concern, or it would crash at 1600 MHz. Yet it is stable, so why is the default clock speed so slow? Considering the phone is perfectly stable at 1600 MHz, would it be possible to O/C my phone to 2 GHz, or would I risk frying my phone if I somehow managed to OC it by that much?
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uhh well.... yea and no. there are a few things you need to understand about microprocessors. no two are alike. they are built on a scale of a few nanometers and any difference causes a significant difference. to keep production numbers up there is a line they have to draw between performance potential and stability. more chips will be stable at lower clocks so they pick an speed they can get a high production number out of. sometimes a whole line of chips is produced with exactly the same core. chips that pass the highest get boxed as the highest performing and priced. chips that dont pass will either have specific features turned off, cores turned off or be underclocked and sold as lower models. in addition to that the top performing models are actually over priced, and often many more pass the tests than they need so perfectly good processors are intentionally disabled to fill the market for lower speed processors, so yes the cpu may be "underclocked" in a sense. but i don't know if that really applies to the infuse because i don't know if there are any chips in the same family that have a higher rated clock speed, if there are they aren't used in phones.
in example, on my pc i have a 3 core processor, it's actually a 4 core and i can even turn the 4th core on in bios, but a certain percentage of that particular model of chip will be unstable with the 4th core active.
another thing to understand is how the clock speed is set. there is a buss and a table of multipliers and dividers. so as one part of the chip oscillates at one frequency the multipliers and dividers say how may times per oscillation the other components go. the cpu speed changes by changing these multiplier values. the problem is that there are only so many multipliers the cpu is designed to use. this is a hardware limitation and can't be overcome so at some point the only way to get more clock speed is to change the buss speed which affects the entire system and will cause instability in most cases. occasionally you can get around this if you change the multiplier values for other componants as well but it's probably not a good idea to mess with it. the hummingbird chip only has multipliers to go to 1600mhz regardless of stability unless you mess with the buss, one developer got the galaxy s to 1700 with buss overclocking but some things didn't really work at that speed and it took a lot of changes to other system clocks. snapdragon chips can go to higher clocks and process numbers better but the hummingbird is better for graphics and multimedia which is more important on a modern phone imho.
so yeah 1600 is it, as far as practicality goes anyway. there are a few infuses that can only go to 1400-1500 as well and galaxy s phones which have the same clock limitations but are only rates for 1000mhz rarely go to 1600, but a few do, my captivate was absolutely peaked out at 1300, believe me i tried to get it higher, i tried a lot of things with voltages to try to get it stable, but even 1300 took some doing. it took a long time before developers even produced a kernel for the sgs that used clocks over 1200 because many of the early builds of the sgs series were much like mine and were not stable at high speeds.

Beautiful. :thumbup:
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