yashsingh1/xdaforums huggingface dataset:
[Xoom General] musashiken:
Hmm, your stress testing seems inaccurate.

I used your values and did a stress test at each frequency for around 10 seconds. No problem. But my xoom restarted just 5 mins later while I was surfing the net.

So I increased each frequency by 25-50 and it stayed stable since then.
[Xoom General] princenoob:
for me i just underclock my xoom to 912mhz. it is almost as fast as 1ghz. and i save battery alot. :)
[Xoom General] lindsaytheflint:
Try bumping up the voltages a little bit at a time, until you find a stable setting. The settings I listed are what are stable for my Xoom (even intensive 3D games), but CPUs vary. What I get, others may not, and others may get better than me.
[Xoom General] lindsaytheflint:
They're not 100%. The longer you stress test, the more likely the CPU is stable, but 10 seconds gives a general idea. If unstable, just do as you did, and increase by 25mv or so.
[Xoom General] lindsaytheflint:
Can you confirm your mV values? -175 sounds like a big saving. Surely your mV is not less than the minimum 770?

What kernel are you using?
[Xoom General] baron von bubba:
do some proper tests to establish how much extra time you will get from a fully charged batt.

i would think its perhaps a tiny bit at most...

the screen would take a huge amount of the batt, the processor would use only a small percentage, so surely cutting a small fraction off a couple of steppings is fairly pointless?
[Xoom General] lindsaytheflint:
1. It depends what you're using the device for. Games, for example, can use a lot of CPU, so undervolting in this instance, will definitely use noticeably less battery.

2. If CPU voltage throughput didn't make any difference, we'd all just run our devices at 1700mhz all the time.

3. With undervolting, I can run my Xoom at the same voltage at 456mhz, as it run at 216mhz. This means I set my minimum frequency to 456 instead, and for the same minimum battery consumption, my device is noticeably smoother.

If you want to know how much extra time you will get from a fully charged battery, YOU do some tests.
[Xoom General] omnia1994:
Yes i m sure. Has been using these settings till now.. no prob at all. Using tiamat stock gpu kernal with moray rom
[Xoom General] Psychokitty:
i agree that during low intensity operation the power savings are probably nearly negligible, but during CPU-intense usage it could save a bit.

I myself am not willing to leave my Xoom on full bore for a series of tests lasting 7-10 hours each just to quantify how much power undervolting can save under super extraordinary circumstances.

But even if the energy savings is an arguable benefit, the reduction in CPU temperature is not. That alone makes this worth doing, IMO.
[Xoom General] omnia1994:
Agree.. after setting it my xoom now has lower temp when playing it
[Xoom General] baron von bubba:
1. yes, battery will be saved, but a "noticeable" difference????

show your tests and results please?

2. nope, that would be stupid.

most wont even run at 1700mhz. and if it did, most ppl wouldnt choose to run at this and NOT because of battery usage.

i have a galaxy s2 and have done tests, undervolted and underclocked against a large overclock and there is very little difference to batt life.

now battery life is a large concern for me, hence the testing of the s2, yet i run my s2 @1500 mhz max 500 mhz min.

oh, and the screen is about a sixth the size so comparatively will use a lot less batt then the xoom.

3. is a fair point...

...as far as running smoother goes, my xoom also is set at 456 min.

but as for saving battery even if the processor was the ONLY thing using the power it would be a saving of less than 10%.

as it is, i think a saving of maybe 2 or 3% is all youd gain under normal use.

about 15 mins on an 8 hour batt.

and no i wont be testing, i have tested enough on my phone so can fairly well see what the results would be.

you are the one posting claims of helping save battery life, so why dont you quantify the savings that we would see?
[Xoom General] musashiken:
I'm sure most of us here just want a better understanding of undervolting as there wasn't any thread about it prior to this. So thumbs up to the OP for helping us to at least start from somewhere.

Your arguments here are pretty pointless really. No one here expects super savings from undervolting and it's understood that mileage will vary with each device. So what some of us want is to at least do something, anything to cut down on voltage. That's why there's an option to undervolt.

Really if you want better battery life, get a battery pack or something. I just want to squeeze as much juice possible only because it can be done, not because I expect my Xoom to last an extra day.
[Xoom General] lindsaytheflint:
1. Yes, a noticeable difference. You ask me to test for you, but refuse to yourself?!?

2. I also have a Galaxy S2, and have done lots of different tests with the battery. If you had done any kind of worthwhile tests yourself, you would know that setting the CPU to 1500mhz max, will DEFINITELY impact the battery if you are performing CPU-intensive tasks, like games. When I go on flights, I like to play games on my phone for a few hours. I set my max CPU to 800mhz in these instances, as it makes a big difference to my battery life, as I've tested many times. You may want to ask yourself the reverse - what performance benefits are you getting from overclocking your CPU from 1200 to 1500???

3. If you want to make up bs numbers, post your test results somewhere so someone can read them (not here - I'm not interested).

Many custom kernels support undervolting (and most SGS2 kernels do), so clearly it's something that the kernel devs feel is worthwhile. Similarly, many people use undervolting on many different platforms, and enjoy the extra battery potential.

I'm not sure why you keep coming back to this thread when you clearly don't have any interest in undervolting. Seems like a waste of everybody's time, and your posts contribute nothing. Find something better to do.
[Xoom General] Psychokitty:
You're being a tool. Obviously undervolting is not for you, so piss off so the rest of us can enjoy the discussion.

lind, I'd be very curious to see data showing how low the voltage can be taken in steps with regards to CPU overclock limitations.

When I was doing this on laptops a decade ago (Pentium Mobile Dothan) there was a correlation between the ability to push the clock and the ability to undervolt, but I can't remember what it was.

If We could generate some more lists, I would put it in a spreadsheet and post it up. :)
[Xoom General] Peterpaulmarie:
Thanks for your hint. I 'll try it.
[Xoom General] baron von bubba:
Hmmmm look up forum in a dictionary...

Explain how this is a disscussion if someone with a differing opinion is told to piss off

Im just saying the extra life is negilable, ffs the background colour of the home screen on the s2 make more diffrence to bat life than undervoltin.

There have been proper tests done, if i could only find the link.

Hmmm, Its funny how someone saying it makes little diff is shot down, but the "ive under clocked a bit and get loads better batt life" are valid comments. I guess fan boys are funny creatures...

Did you know if you hold the device tottaly still while using it, you get loads more batt life, as the accelerometer isnt wasting power.... try it, i get shed loads more batt...
[Xoom General] baron von bubba:
ok, so after getting told to piss off i thought id dos some tests, just quick tests, so only rough figures.

i ran 3 x 30 minute stability tests with the screen on. (using app "stability test")

governor set to performance, thus locking the clock speed at max.

1st run @ 1504 - stock volt.

battery went from newly charged 100% down to 88%

difference 12%

(screenshot time 02:55:11)

2nd run @ 1000 - stock volt. (1100)

battery went from 88% down to 80%

difference 8%

(screenshot time 03:25:56) 00:30:45 later

3rd run @ 1000 - UV @ 1000

battery went from 80% down to 71%!!

difference 9%!!

(screen shot time 03:57:18) 00:31:22 later

just a rough test...

...but at least i could be bothered.

anybody else wanna offer some more "results"??
[Xoom General] lindsaytheflint:
The old "I found a link that proves you wrong, but don't know where it is" line huh? Yeah, well I found 10 links that prove you wrong, and I don't know where they are, so I win.

And no-one made any claim about "loads better batt life". Musashiken summed it up right: "No one here expects super savings from undervolting and it's understood that mileage will vary with each device. So what some of us want is to at least do something, anything to cut down on voltage. That's why there's an option to undervolt."

However, you've posted some results (albeit VERY rough), so I'll do the same. I'll run some extended tests, and post back here in a couple of days.
[Xoom General] baron von bubba:
excellent.

surly only the max and min voltages would be the only ones to matter anyhow, the device seems to ramp up thro the steps and spend very little time at the middle steppings...

oh and "stabilitytest" will do test while going up and down the processor freqs, maybe a bit easier to test ppls settings than locking each stepping out individually to stress test it
[Xoom General] lindsaytheflint:
Tests should be locked to the max frequency only (i.e. min & max the same), otherwise the testing is not accurate due to the potential for CPU frequency fluctuating.

Again, best to lock the frequencies when testing different voltages, otherwise if it hangs, you don't know which frequency is the problem, and also it will not necessarily stop on each frequency for long enough to know whether it is stable or not.
[Xoom General] lindsaytheflint:
Performed some battery performance testing by doing the following steps:

1. Set the screen to not turn off, and brightness to 10% (screen needs to be on to keep the stress test running, and brightness low to minimise the battery drain of the screen, as that's not what we're testing).

2. Disabled all network connections (WiFi, Bluetooth, Data, GPS) to minimise battery drain by other factors.

3. Closed all other apps, and did not use the Xoom at all during the tests.

4. Charged Xoom to 100%.

5. Set CPU speed to 1504mhz using SetCPU (both min & max frequencies the same for accurate testing).

6. Unplugged the Xoom.

7. Ran "Stress Test" for 2 hours (give or take 20 seconds).

I performed the above steps for both stock voltage, and undervolted voltage. Results as follows:

1. For stock voltage (1325mV on Tiamit Tachi kernel), battery life went down to 62%.

2. For undervolted voltage (1175mV, which is nice & stable for me), battery life went down to 72%.

Findings:

I was expecting battery savings, but not quite this much.

Standard voltage (at 1504mhz) at this CPU load, drains at about 19% per hour.

UV voltage at this CPU load, drains at about 14% per hour.

Standard voltage at this CPU load, the Xoom would drain battery entirely after about 5.26 hours.

UV voltage at this CPU load, the Xoom would drain battery entirely after about 7.14 hours.

In addition to the battery savings, the Xoom was only slightly warm after the UV tests, but very warm after the standard voltage tests. (Standard voltage test was performed first.)

Note: For general usage (email, browsing, basic apps & widgets), the CPU is not as heavily used. But in situations where the CPU is heavily used (such as intensive games), these results show there is significant potential for battery savings.
[Xoom General] lindsaytheflint:
The 1st test has a different frequency to the other 2 tests, so is invalid.

As for the 2nd and 3rd tests:

The were not both started at 100% battery. Batteries do not necessarily decrease at the same rate all throughout the charge.

If an UV test performs worse than a stock voltage test, then the testing is DEFINITELY flawed. Less voltage cannot use more battery. Think about it.

You make no mention of your network connections, other running apps, and other factors that would be eating your battery life.

30 minutes is not enough for a test of large battery such as the one in the Xoom.
[Xoom General] e.mote:
I just read the tail end--post #31 specifically--so excuse if I've missed anything, but the conclusion drawn from your test is flawed.

CPU is only one of several components that use power. By minimizing power-use of other components, the test exaggerates the resultant change. Secondly, by running "stress tests", ie emphasizing CPU use, the exaggeration is further exacerbated.

A more correct method is to set all the components at their normal power level, then devise a typical-use test suite that can be replicable for multiple runs.

BTW, you should notice something is suspect when the your finding shows savings that result in a better than 100% power efficiency, ie,

Power saved from voltage decrease, as percentage,

(1325 - 1175) / 1325 = 11%

Power saved per battery use, as percentage,

(38 - 28) / 38 = 26%

Even if the CPU were the sole component using power, which it isn't, the resultant power saved in battery life cannot be larger than the voltage decrease (in %).

Lastly, as you yourself said, battery discharge rate is not linear for the whole cycle, so comparison of X vs Y% battery remaining isn't accurate, as that assumes a linear relationship. More accurate would be to do a battery run-down test, with an automated typical-use benchmark, then comparing times when the unit shuts down.
[Xoom General] lindsaytheflint:
Actually, you missed the tail end of post #31:

"Note: For general usage (email, browsing, basic apps & widgets), the CPU is not as heavily used. But in situations where the CPU is heavily used (such as intensive games), these results show there is significant potential for battery savings."

Undervolting only affects the CPU power consumption, so that's the only thing I'm testing. We all know that things like screen, WiFi, & data, will use more power than CPU, but they're not what this topic is about. They're not relevant to undervolting.

I disagree. This post is to show potential battery (& heating) savings from undervolting the CPU. In terms of real-world usage, that would vary so much, that those kind of tests would be pretty much pointless. I'm only trying to show potential savings from the CPU aspect. How much that will benefit in real-world usage, will vary.

I don't think it's as simple as that. For example, batteries usually retain charge less effectively in high-temperature scenarios. That could be a factor in my results - my device was much cooler when undervolted. And given that the only variable that I changed during my tests was the CPU mV, I'm not sure how you could negate it. Both tests (UV & stock) were performed twice with similar results, and the device was unused during the time. I'm basing this on numbers, rather than guesswork.

I agree with this - the longer the test, the better the accuracy, but I don't have the time for that kind of thing. I struggled to find time for this as it is. I ensured that both sets of tests were charged to 100% before execution, to reduce the potential for battery discharge rate differences. You're more than welcome to do some tests and post your results.

This thread is not to say you will get x% battery savings by undervolting, it's a howto, with a sample of demonstrated battery savings in an extreme circumstance. I've tried to make this clear, but I'll try again: In general usage, battery savings from undervolting may be negligble. In high-CPU-usage scenarios, such as intense gaming, you may potentially experience significant battery savings. It won't decrease battery consumption by your screen, GPU, network connections, SD card, etc - just the CPU.
[Xoom General] e.mote:
>Undervolting only affects the CPU power consumption, so that's the only thing I'm testing...[The other components are] not relevant to undervolting.

That's not the conclusion you drew, which directly extrapolated savings to increases in battery life. As already said, battery life encompasses use from all components and not just CPU. If you want to claim this--X voltage decrease leads to Y increase in battery life--you would have to normalize CPU power-use as part of overall system in a normal use-case, not a distorted use-case that have other critical components disabled.

>I agree with this - the longer the test, the better the accuracy, but I don't have the time for that kind of thing.

I'm afraid I don't think much of this excuse. Regardless, the systemic distortions mentioned above far outweigh the non-linear discharge distortion. Think about it for a second--an 11% decrease in CPU voltage leads to a 26% decrease in power use. It's nonsense, your speculation of better thermal efficiency notwithstanding.

>In general usage, battery savings from undervolting may be negligble. In high-CPU-usage scenarios, such as intense gaming, you may potentially experience significant battery savings. It won't decrease battery consumption by your screen, GPU, network connections, SD card, etc - just the CPU.

This would be obvious enough without any testing. The reason for testing is to find how significant the savings are, for the device as a whole--as that's what you're using; you're not using just a SoC. Your flawed methods shed no light on this aspect.

My opinion is that it's much less significant than what your findings portray, likely not enough to incur the potential system instability. Given the more-or-less beta status of both the Android OS and apps as a whole, with their occasional FCs, it would be a nightmare to troubleshoot whether a FC is a result of software or of undervolted hardware. If your time was at a premium as indicated, there are better avenues to optimize the device for greater efficiency, eg finding & removing apps that hog CPU cycles. Of course, different strokes and all that.
[Xoom General] e.mote:
>Suffering from MPD, or just a ftard?

When you can't answer rationally, call people names. Typical net response.

You post your findings on a public forum, which I found as flawed and stated so. Your excuse is that you "don't have time" for a more accurate test, a test which found 11% voltage decrease leads to a WHOPPING 26% DECREASE IN OVERALL POWER USE. Any idiot can see this as laughably outrageous. Except for you, of course.

>I was surprised at the high level of battery savings too. But given that A. The only variable that changed was the CPU voltage, B. The tests were performed otherwise identically, and C. Each test was performed twice with similar results, the only conclusion I can come to is that the CPU voltage makes a big difference.

That's because you're too wrapped up in trying to justify your hobby of undervolting to understand the ramification of system testing. The CPU is a part of the whole, and cannot be tested in isolation. You cannot disable stuff and then claim X increase in battery life. You cannot ignore things like nonlinear discharge curve and claim you "don't have time for accurate testing". It's that simple.

I'll leave the rest of your enumerated gobbledygook for you to revel in.
[Xoom General] lindsaytheflint:
It's hardly "rational" to ignore logic and evidence, based on your own guesswork rather than any kind of intelligent analysis. As I said, if you have results that prove otherwise, then post them. No tests or results, means you're just guessing, and not very well.

You continue to ignore facts and figures, and just throw around pointless statements. You don't back anything up, and you haven't disproven anything.

This is hardly my hobby - I only post on these forums when I have information to contribute. Not all of us use these forums as a substitution for any real-world activities. I've wasted far too much of my time on you.

If anyone else is interested in undervolting, try to weed through these posts and stick to the actual bits of useful information, and ignore any baseless arguments.
[Xoom General] musashiken:
Instead of criticizing others, why don't you do your own testing? Pointing out the fallacies in others' methodology is fine and all but in the end you're just all talk. At least the OP did attempt to do something and shown some results.

All your theory in "nonlinear discharge curve" and stuff means balls to the rest of us who don't really give a damn seriously and I don't even understand half of what you are saying.

I came here to find out how to undervolt my Xoom, not to read some bunch of electric hocus pocus.
[Xoom General] Audionut11:
I've only just briefly skimmed the last few posts, so sorry if I missed something important.

lindsaytheflint, you're tests are spot on. When ascertaining the affects (of anything basically), you must rule out all external influences.

So running the tests as you have with all the other battery draining services disabled is how it should be done.

If a user decides that they want to convert your percentage results into a total system (ie: bluetooth, wifi etc left on) result, then the onus is on them. Unfortunately, some users are either, lazy, retarded, trolls or whatever, and expect all the results to be handed to them on a platter without making any effort on their part.

The only thing I would mention though. Even though the 456mhz frequency runs at the same voltage as the 216mhz frequency, power usage will still be greater for 456mhz.

edit to clarify: Even though 456mhz is asking for the same amount of Volts, it's doing more work (as a result of processing faster) and hence chewing more amps (power).

Having said that, I would imagine that the total system power increase from running at 456mhz compared to 216mhz (at the same voltages) would easily be less then 1%. Probably something like .01% or less.

So the benefits seem to outweigh the cons.

I would still run a screen off profile at 216mhz though, to save every last ounce of juice.

edit 2: Just another quick thanks. As you seem to be copping a lot of crap for simply trying to explain things and help.
[Xoom General] lindsaytheflint:
Thanks Audionut.

I had wondered about whether different frequencies at the same voltages (like 216 & 456) would use different power consumption. Interesting.
[Xoom General] e.mote:
>All your theory in "nonlinear discharge curve" and stuff means balls to the rest of us who don't really give a damn seriously and I don't even understand half of what you are saying.

You're on the Internet where every piece of info is just a few key clicks away. Exercise the privilege.

http://google.com/search?q=li-po+discharge+curve

http://www.fmadirect.com/lipo_handbook/FMA_Lipo_Handbook_Section3.htm

Battery (li-po) chemistry is a complicated subject. Your typical battery indicator is only an approximation, and not an accurate one for point-to-point measurement. Per above, the discharge rate varies greatly depending type of load, as well as other factors like ambient temp. And as can be seen, it is non-linear (not a straight line).

That's why it's meaningless to do a time-specific test, then proclaim X battery savings based on the battery indicator. The error is further compounded when the load is not from normal use--disabling system components and stressing CPU-only load.

Let's look just at the non-linear discharge issue. Here's a more simplified pic for li-po discharge:

As you can see, there's a pronounced initial drop-off from a full charge, a gradual decline in the middle portion, and a steep drop-off at the end.

Even assuming the battery indicator is dead-on accurate (which it isn't), by taking readings from full-charge down to the 70-60% level as what the OP did, he is accounting mainly for the initial drop-off and not the rest of the curve. By extrapolating from only this initial portion, his findings of changes in battery indications would be exaggerated. Hence, my advice to do full run-down tests, which the OP conveniently ignores in favor of pratty name-calling.

I'll leave the other args raised for interested readers to pursue. Suffice it to say that an engineering degree isn't required to understand that 11% decrease in CPU voltage can never lead to 26% decrease in overall power use. It's hocus-pocus. Anybody can throw out a bunch of numbers.