Database Users

Overclocking N1

You can overclock n1 only to 1.190ghz, while desire hd 1.9ghz and the htc desire Z (G2) 2.0ghz. Does N1 has to old cpu?
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Sent via the XDA Tapatalk App with my Sexy Nexy

Yes. 1st Gen snapdragon
Sent from my Nexus One using XDA App

if you want to OC you N1 go and OC you Desktop is the best choice

Why would you wanna over clock your phone? I have my N1 clocked @ 691 and works really fast with the MIUI rom and battery performance is better than stock. I'm not a fan of custom rom & rooting but I been pretty pleased so far. overclocking the nexus one will drain your battery like crazy plus the 1st Gen of snapdragons weren't as good with graphics as the A4chips and humming birds.

i have mine underclocked too and it works fine. try going a step further and underclocking it to like 422 when it's sleeping/standby. it'll help your battery

josemedina1983 said:
Why would you wanna over clock your phone? I have my N1 clocked @ 691 and works really fast with the MIUI rom and battery performance is better than stock. I'm not a fan of custom rom & rooting but I been pretty pleased so far. overclocking the nexus one will drain your battery like crazy plus the 1st Gen of snapdragons weren't as good with graphics as the A4chips and humming birds.
Click to expand...
Click to collapse
The connection between clockspeed and power consumption is not as strong as you think. But without a doubt it has an influence. Much more important is the voltage. If you "undervolt" the Nexus One CPU you can even get better battery live with higher clockspeed.
And if you use a tool to change the clockspeed depending on the situation (display on/off, battery % left, workload) and undervolt the cpu you can safe A LOT of juice.
With Wildmonks kernel, MIUI and SetCPU I get a much better lifetime than ever before even though my Nexus runs at 1152MHz.

Actually, the frequency makes a BIG difference in power consumption. Think of it this way - each clock causes changes propagating in transistors, which are the actual power draw. More clocks = more changes = more power drawn. As easy as that.
So, having 10% higher frequency and 10% lower voltage compensates each other.
Nexus has examples that overclock to 1.5GHz when overvolted, like Desire Z and Desire HD (both of those have to be overvolted to go up stable from 1.2GHz). Most of Nexus Ones fail when overclocking and don't reach higher than 1.2GHz, but it might be not because of the CPU, but because of other devices on system board.

Generally, it is only when you change the voltage (which is required to stabilize the higher frequency) that you see noticeable differences in battery life.
Jack_R1 said:
Actually, the frequency makes a BIG difference in power consumption. Think of it this way - each clock causes changes propagating in transistors, which are the actual power draw. More clocks = more changes = more power drawn. As easy as that.
So, having 10% higher frequency and 10% lower voltage compensates each other.
Nexus has examples that overclock to 1.5GHz when overvolted, like Desire Z and Desire HD (both of those have to be overvolted to go up stable from 1.2GHz). Most of Nexus Ones fail when overclocking and don't reach higher than 1.2GHz, but it might be not because of the CPU, but because of other devices on system board.
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Click to collapse

willverduzco said:
Generally, it is only when you change the voltage (which is required to stabilize the higher frequency) that you see noticeable differences in battery life.
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Click to collapse
Ok, some additions required.
Leakage is also dependent on power, and the dependency graph isn't linear - and starts breaking upwards at some point, usually being a tad above the max designed voltage.
Going down in voltage makes leakage change approximately linear, and doesn't affect nearly as much as going up.
Overclocking will draw power just as I noted above - exactly with the same percentage difference - only when the clock is reaching the overclocked area, which happens only when you're playing games or doing CPU-intensive tasks.
Undervolting will affect leakage, which happens 100% of the time.
So yes, when running in dynamically scaled environment, undervolting has more effect than overclocking. On desktop PC, running the same clock frequency constantly, the effect is the same.

Very True. And I wasn't saying that overclocking, while at the same voltage, didn't draw ANY more power... I just am trying to say that (for example in this graph) overclocking only has a small effect on power draw until you actually change the voltage. In that same example, going from 3.4 to 3.8 GHz only adds about 6% current draw while at the same vCore, while going up a similar amount in clock speed.
I'd even wager to say that if you're slightly under-volted and as heavily overclocked as you can go at that given voltage, you'll save some trivial amount of power versus stock because of the fact that voltage affects power draw significantly more than clock speed. I would also wager that if you are at an overclocked speed and are at stock voltage, the amount of current and power draw will be almost indistinguishable to the end user, since things like display will almost always use much more power if the display is on for any appreciable amount of time.
Jack_R1 said:
Ok, some additions required.
Leakage is also dependent on power, and the dependency graph isn't linear - and starts breaking upwards at some point, usually being a tad above the max designed voltage.
Going down in voltage makes leakage change approximately linear, and doesn't affect nearly as much as going up.
Overclocking will draw power just as I noted above - exactly with the same percentage difference - only when the clock is reaching the overclocked area, which happens only when you're playing games or doing CPU-intensive tasks.
Undervolting will affect leakage, which happens 100% of the time.
So yes, when running in dynamically scaled environment, undervolting has more effect than overclocking. On desktop PC, running the same clock frequency constantly, the effect is the same.
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Click to collapse

Jack_R1 said:
Actually, the frequency makes a BIG difference in power consumption. Think of it this way - each clock causes changes propagating in transistors, which are the actual power draw. More clocks = more changes = more power drawn. As easy as that.
So, having 10% higher frequency and 10% lower voltage compensates each other
Click to expand...
Click to collapse
I wouldn't call 10% more peak power consumption big if you take in account that the cpu is only running at the max clock speed a very small amount of time. 90% of the time the device is sleeping anyway and even if it's not you barely need the max clock speed. But if you do you will recognize the difference.
On the other side the reduced voltaged can safe you power all the time.
willverduzco said:
I'd even wager to say that if you're slightly under-volted and as heavily overclocked as you can go at that given voltage, you'll save some trivial amount of power versus stock because of the fact that voltage affects power draw significantly more than clock speed. I would also wager that if you are at an overclocked speed and are at stock voltage, the amount of current and power draw will be almost indistinguishable to the end user, since things like display will almost always use much more power if the display is on for any appreciable amount of time.
Click to expand...
Click to collapse
That's exactly what I experienced.

Pommes_Schranke said:
I wouldn't call 10% more peak power consumption big if you take in account that the cpu is only running at the max clock speed a very small amount of time. 90% of the time the device is sleeping anyway and even if it's not you barely need the max clock speed. But if you do you will recognize the difference.
On the other side the reduced voltaged can safe you power all the time.
Click to expand...
Click to collapse
Yes, you're right, and that's why I corrected myself in my second post. I totally forgot about the frequency scaling.

Off topic, but this is why I love XDA. Rational debate over a subject by intelligent people, where there usually isn't flaming. Thanks added to the two of your posts.

[Q] Undervolting vs. Battery life

Hi, I spend last few days optimizing voltage table on my Desire and it left me wondering.
I bumped into several situations where 2 or 3 frequencies would be stable on the same voltage level. My question is, theoretically, if 300MHz would use the same voltage as 800MHz, would the power consumption increase proportionally or would it remain fairly similar?
Seeing that 300MHz would need more burn time at the same voltage to complete a task that 800 MHz would do in fraction of that time and then idle, this leaves me puzzled. Is it better to always use highest frequency of the group with same voltage for better efficiency? Or does the slower frequency actually consume less power even though it has to work longer and uses the same voltage?
Please enlighten me or discuss

I would also like to be enlightened on this.

AFAIK your assumption is on the right track, get the job done as quick as possible & get back to idling...
Slightly off topic, but somewhat relevant
byrong did a great write up on the effects of cpu speed vs screen brightness power consumption here that may be be of interest...

Interesting but still doesn't answer one question:
If my 245, 368 and 768MHz would be stable at the same voltage, does it matter if I set 768MHz as my minimum/idle frequency instead of 245MHz? Would is consume more power in the long run say on conservative governor?
And what about the screen-off profile? Consider a scenario when I'm playing an MP3 while screen is off and the player will still take a lot of CPU power to pre-buffer the song, apply equalizer, post-processing etc. Now would that nearly constant burn theoretically consume more power on the 245MHz or 768MHz? It still has to do the same work and 245MHz should just have higher constant load, right?
And how about complete idle. Does it really matter if I idle on 245 or 768 MHz if the voltage and actual work done is identical?
This is I'm sure something everybody is asking but nobody knows the real answer. Unless I'm speaking utter rubbish it's perhaps time to run some tests.

Even if the voltages are the same for different frequencies, I'm sure higher frequencies draw higher amounts of current (as shown in byrong's research, although his voltage tables were not stated). If you change your min cpu freq from 245 to 768 MHz I'd almost guarantee more power consumption, even when idle. I could be wrong though. If you're so curious, why don't you try and post back?

I might be wrong but my $0.02
From what I can remember in class, Power = voltage x current
To do the same amount of work, supplying lesser voltage would mean more current is consumed. That said, if less work is being done at the same voltage, less current would be consumed.
So running the CPU at a slower clock cycle means less work is being done, so less current consumption, compared to running it at full 768MHz.
I think ... ;p

Well I think I will make some empiric testing as soon as I find a way to log current current (yea funny ) to a file.
Even if your $0.02 are right, you're still talking about drawing less current over longer time or more current in a short burst. Of course there are apps like games that will probably take as much horsepower as they can get for redrawing the screen - in that case lower constant frequency is better, because higher frequency would actually have to do more work - drawing more FPS just because it can. For minimum frequency the situation is completely different as the apps only require bursts of workload.

nik3r said:
Well I think I will make some empiric testing as soon as I find a way to log current current (yea funny ) to a file.
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Click to collapse
I thought you read waydownsouth's link?
In the methodology section byrong states he used CurrentWidget to log current over time. You can also use Battery Monitor Widget.
By the way, his methodology is pretty excellent as it minimizes as many variables as possible, and he wrote his own script to keep the cpu working at a controlled rate. I think at a minimum, you should put the phone in airplane mode while conducting the tests.

Does cpu frequency affects battery life?

The question is simple, the higer the freq. the more battery consumption? i am asking because i cannot see any difference from 1.4GHZ to 1.0GHZ, the battery consumption is the same under oxygen and francos kernels. i would be grateful if the experts would give us some advise or their opionion. I know it is subjective but i would like a second opinion.
Thanks alot guys

If you look with any cpu spy app, you cab see on what clock the processor is used. I mainly have it the lowest and sometimes higher. When you change the max, it should still automatically choose what clock is used, so battery should last as much as before, if not used in high clock.
Sent from my Huawei u8800 using XDA App

Invicta said:
The question is simple, the higer the freq. the more battery consumption? i am asking because i cannot see any difference from 1.4GHZ to 1.0GHZ, the battery consumption is the same under oxygen and francos kernels. i would be grateful if the experts would give us some advise or their opionion. I know it is subjective but i would like a second opinion.
Thanks alot guys
Click to expand...
Click to collapse
Probably not much difference, when you overclock, think the cpu voltage remains the same as it is on 800mhz... And the highest cpu freq is rarely even at use...

Invicta said:
The question is simple, the higer the freq. the more battery consumption? i am asking because i cannot see any difference from 1.4GHZ to 1.0GHZ, the battery consumption is the same under oxygen and francos kernels. i would be grateful if the experts would give us some advise or their opionion. I know it is subjective but i would like a second opinion.
Thanks alot guys
Click to expand...
Click to collapse
Well, thanks to most devoted users of U8800, we have somewhat better speed+battery life than stock also. To answer your question, yes depending on your activity the frequency have some impact, but overall shouldn't be huge in change, for example from .800 to 1.0GHz will not affect so much in daily use. However from .800 to 1.5GHz would make a somewhat huge gap difference. This doesn't mean it will drain faster if you do same activity as with .800 to 1.0GHz, for example check the watch, answer sms or few "entertainment" breaks. Only when using the phone over a longer period of time that's when you will notice the change of battery life with different frequency. Hope it clears up most hums and huhs for you. I am pretty sure some expert within this field will give a better explanation than me.
Bye~

higher freqs uses more energy, but lower uses less energy but do things slower (so energy consumption is longer). ALSO imo - if you set cpu to 1Ghz the lowest value so it always is 1ghz - it will not consume the same amount of energy if it's in idle mode - it's like your laptop - if cpu is working only in 4-7% of it's power - then the power consumption is lower no matter what freq - how do we know that? - because of heat - the more heat you get - the more energy was used. and when cpu is idle - it will not be hot.
So the answer is - if it saves then in VERY minimal amounts. But even so - i use min freq - 360mhz. it's good for me i do not get any lag so i use it.

I use the "Root System Tool Free", option CPU and I see the graphics of all clocks.
For ex. now at 245 mhz ->46%, at 368 ->10%, at 768 mhz ->18% .... and at 1612 mhz -> 1,8%, at 1804 mhz ->4,9%. Not very mutch use at 1804.
Oxygen-test-140911 + Franco.Kernel1709#1. Clock at 1804 Mhz by Menu-settings-cpu ... and smartassV2 (no profils).
The battery, I charge it all 24 hours. But I like my work... and testing things. When then will dead...I see...

ValenteL said:
I use the "Root System Tool Free", option CPU and I see the graphics of all clocks.
For ex. now at 245 mhz ->46%, at 368 ->10%, at 768 mhz ->18% .... and at 1612 mhz -> 1,8%, at 1804 mhz ->4,9%. Not very mutch use at 1804.
Oxygen-test-140911 + Franco.Kernel1709#1. Clock at 1804 Mhz by Menu-settings-cpu ... and smartassV2 (no profils).
The battery, I charge it all 24 hours. But I like my work... and testing things. When then will dead...I see...
Click to expand...
Click to collapse
cpu spy is more pretty, anyway all those apps just reads text file of cpu stat and that's it

Tommixoft said:
cpu spy is more pretty, anyway all those apps just reads text file of cpu stat and that's it
Click to expand...
Click to collapse
Thanks
But I like more the Root System Tool, because has also a Linux Console. I use it when I want make some cmd's Linux in #. I don't like the Terminal Emulator.

Well, there is a "catch" somewhere in there. The frequency does indeed affects the power consumption of the CPU and greatly at that too! But the thing is, your CPU is not the worst enemy of your battery life. Even though CPU consumes more power in higher frequencies, it still can not compete with what your screen LEDs or your GSM module or your GPS chip consumes leisurely. So, if you're looking at the overall picture -meaning if you're wondering if it will affect how long you'll be able to use your battery in your phone- the answer is, "yes but not so much". Especially if you're switching the CPU frequency based on the demand (like using smartass or on-demand governors)
Here are the thing that sucks your batteries life juice like a vampire :
Your Screen (especially background LEDs)
GSM module (talking, using GPRS/Edge/3G network communication)
GPS chip
Wireless module (this also includes Bluetooth, even though it does not consume as much as Wireless network access but everything is relative -think about playing music through A2DP headphones compared to having your wireless network active but not using it much-)
(oh yes, I love to use lots of parenthesis -and even this hyphenation thingy- )
Correct me if I'm wrong about anything by the way ..
Regards ..

I did some experiments with a msm8250 a while back and there's a graph here:
http://forum.xda-developers.com/showpost.php?p=14324649&postcount=3786
msm7x30 should be fairly similar though the graph is probably shallower since it's a smaller process size.
The CPU uses no power when it's not in use, even with the display on, the CPU is powered down completely when idle (power collapse).

[REF] Battery Drain Benchmarks

Spreadsheet of the Battery Drain Data
BATTERY DRAIN BENCHMARKS
VIDEO of how it's done! (Do NOT try it yourself!)
NEW: Lab study done by nathanson666 see here and featured on the XDA's portal and twitter here.
Summary of Results
#1 - With screen on, if the processor is Idle, 100MHz saves the most power.
#2 - Regardless of your choice of governor, even with extreme undervolting, you are not going to be able to increase your battery life by more than 2%. (Click here for explanation.)
For the instability introduced by UV, it seems a 2% increase in battery life isn't really worth it! REMEMBER rebooting uses so much power, a single one would more than undo any savings made by UV.
#3 - The most power saving governor is Ondemand. If you need a high performance governor, use smartassV2, which offers some battery savings.
#4 - This is one point that everyone ought to know, but I'm including because many people seem to believe in myths: if the screen is off, and the CPU is not active, neither deep idle nor UV will have any impact on battery life.
#5 - The matr1x kernel by mathkid95 mainly saves power through UV of the INT voltages. You may need to raise these if you have freezes/reboots with your phone (in addition to raising the ARM voltages). I found that a maximum of 1 mA can be saved through INT UV, regardless of whether the CPU becomes idle (or with screen off in deep idle), so this is a constant saving. However, it is a very small saving, and doesn't apply if the phone is asleep. Remember, reboots cost more juice than UV can ever save.
#6 - If you have an amoled display, black saves a great deal of power. After that, red. If you have a black and red theme, this is saving you power!
#7 - If you are determined to UV, I found that my phone would become unstable with UV settings that were fine when the battery was fully charged. So check what UV your phone can handle when your battery is nearly empty. Again I say: Because of the high likelyhood and massive battery drain that comes with a reboot, I highly recommend you DO NOT USE EXCESSIVE UV. Also remember, even with extreme UV, you will not increase battery life more than 2%
#8 - I found that with bluetooth or GPS preventing the TOP=OFF state, there was no additional power saving from Deep Idle, i.e. the TOP=ON state does not save power.
#9 - Kernels with the 65 fps hack will cause the screen to drain about 10% more power compared to the usual 56 fps.
#10 - Conservative does not save power! For further details and exceptions, refer to my new thread: here.
#11 - This is just general advice: if you are having very poor battery life, have you tried turning auto brightness off? And if you've got no reception, you might as well be in airplane mode, because searching for reception also eats battery.
#12 - If your phone can't handle OC (or UV for that matter) it's because components in general are built to cost, which means factoring in tolerances, and every chip is made as cheaply as possible within the specified tolerances. Outside of those tolerances, whether your chip can cope or not is unfortunately down to the whether you got lucky with the individual device that dropped off the manufacturing line.
ARM document on A8 fault tolerance: http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0344k/Babhjhag.html
In fact I measured how UV in particular can cause errors, and saw in action the A8 using MORE power to correct the errors. From my spreadsheet:
At 100Mhz
mV 1500 4.92mA
mV 950 2.83mA (default mV)
mV 800 2.58mA (UV saves some power)
mV 750 2.96mA (Extreme UV uses MORE power)
Same test but with Deep Idle enabled:
mV 1500 1.91mA
mV 950 1.49mA
mV 800 1.29mA
mV 750 1.49mA (Same result again but with DI enabled)
Referenced from my spreadsheet starting row 41.
Recommended reading: http://everything2.com/title/wafer+yield
Stock voltages for reference:
ARM
1000MHz @1250mV
800 MHz @1200
400 MHz @1050
200 MHz @950
100 MHz @950
INT
1000MHz @1100
800 MHz @1100
400 MHz @1100
200 MHz @1100
100 MHz @1000
Summary of Power States by tchaari (thanks!)
After research, and some explanation from Steve Garon, it is clear that Deep Idle & CPU Idle are two completely different things:
1) Three main CPU states are implemented in the standard android kernel: NORMAL, IDLE and SLEEP
2) Ezekeel added an intermediate 4th state: Deep IDLE. This saves more power but only when the processor has a background task to run while screen is off. Bedalus proved here that it really saves a considerable amount of power in particular cases (e.g. music playing when screen is off). A minority of users are reporting some slight instabilities with it, but they may in fact be caused by things other than deep idle.
3) The CPU IDLE backport is a replacement of the standard android kernel drivers used to put the CPU in idle/sleep states by the new ARM methods integrated in the linux 3.2 kernel. This backport is theoretically supposed to improve battery life (with just the basic 3 CPU states). It is 100% stable but no power saving has been shown either in bedalus' amp meter measurements, or Harbb's overnight drain tests.
Where did the other benchmarks go?
All ICS ROM Benchmarks: this thread
Kernel Features and Benchmarks: this thread
CPU Governors and I/O Schedulers: this thread
Power Saving Governors: this thread
Thanks to all the developers, and a big shout out to: Harbb for his dedicated testing; tchaari for his motivation, great ideas and inspiration; jcolinzheng for the idea to test Deep Idle at fixed frequencies (genius); aLNG for links to interesting and useful articles; Steve Garon for demystifying esoteric kernel technicalities and his excellent kernel itself; everybody else who helped; and of course Ezekeel for making Deep Idle work, and for a stimulating debate!

Harbb joined in doing specific battery tests, using the phone's battery graph. This is based on the phone's own readings (State of Charge or SoC for short). It's not very accurate for an instant reading, but over time, it does become more and more accurate. Therefore, Harbb conducted some very long (10 hour) tests. To improve accuracy further, he waited for the level of charge to drop to around 80% before each test. This eliminates the another source of inaccuracy, that the first 10% of the battery tends to deplete rather quickly (due to normal wear and tear over its lifetime). In fact, I use Ezekeel's Battery Life eXtender (BLX) to stop the phone charging early (at a user defined level: I prefer 90%) to help slow the deterioration of the battery's maximum capacity by preventing heat damage caused as the battery tries to absorb the final dose of charge above 90%.
Harbb's Data
Harbb's spreadsheet
Here's a summary of Harbb's 10 hour test findings, in order of best battery drain:
- 15% - SmartassV2 with DI
- 16% - Conservative with DI
- 21% - Lazy with DI and SOMF
- 23% - Lazy with DI
- 36% - Conservative
- 39% - Lazy
- 39% - Lazy with CPU IDLE
- 44% - Lazy with Eugene's DIDLE
- 48% - Lazy with Eugene's DIDLE and SOMF
[where DI means Ezekeel's Deep Idle, and SOMF indicates that Screen Off Max Freq was enabled]
Power Misconceptions
1st Misconception:
There is a misconception about about 200MHz using the same power as 100MHz because the voltage is the same. There is an approximate formula for CPU power consumption:
CPU Power Draw = C x F x V^2 (where C=capacitance, F=frequency, and V^2=Volts squared)
Capacitance is a constant, so we can ignore it. Let's fill in the values for the lowest and highest frequencies:
100 MHz V=0.95 so V^2=0.9025
1000 MHz V=1.25 so V^2=1.5625
So this shows we have roughly an extra 70% power drain due to the voltage increase. However, the maximum frequency is 10 times the minimum, i.e. a 900% increase. So the dominant factor in CPU power drain is in fact the frequency. Roughly speaking, the frequency has 13 times more influence over the power drain than the voltage.
Therefore, the governor that keeps the frequency as low as possible for as long as possible will save the most power. This appears to be consistent with Harbb's finding that conservative saves the most power.
2nd Misconception:
Some people say that if they UV they can play a game on their phone for an extra hour. The most you can get from UV is 2% extra battery life (and it is not worth the reboot risk).
See post #4 for calculations based on the actual measurements taken from the phone.
Here is a more academic proof using the same formula from the 1st misconception:
CPU Power Draw = C x F x V^2 (where C=capacitance, F=frequency, and V^2=Volts squared)
Capacitance is a constant, so we can ignore it. Let's fill in the values for just the highest frequency with the stock voltages and then an extreme undervolt:
1000 MHz V=1.25 so V^2=1.5625 (stock volts)
1000 MHz V=1.2 so V^2=1.44 (the most UV my phone can handle with a fully charged battery)
This is an 8% saving. Happily, this exactly matches what I measured in the real test (see cell F62 in the spreadsheet).
Remember, only the CPU is saving 8%, the screen being on uses about 4 times as much power as the CPU even at its highest frequency. This reduces the power saving to at most 2%.
I am of course assuming the screen is on. For most users, this is correct, as their processor will not be under a heavy load unless the device is in use, and this almost always means the screen is on. If anyone can think of any circumstances where the CPU is under a heavy load, but the screen is off, and show that this happens to all users a high enough proportion of the time to be relevant to this calculation, please let me know. [/far fetched caveat]

Testing Methodology
Two videos are available, and note, a circuit diagram of test now linked within the battery benchmark spreadsheet. I've decided to share it publicly as I've now set up and run this test three separate times, with no major problems. So I've reclassified it from utterly reckless, to merely dangerously stupid. Do not under any circumstances try this with your own phone! You have been warned!
You cannot trust battery monitor widget. (More on that in the 4th post)
Here's a way to test Deep Idle without rewiring your phone:
Note - SOMF means Screen Off Max Frequency
Setup must be identical (apart from SOMF). Install battery monitor widget, set history update rate to 10 minutes (not particularly to monitor the battery, but just to act as a timer). Set to run without widget. Turn off all radios, turn off sync, turn off location services, put in airplane mode. Turn off any of Ezekeel's mods excepting (Deep Idle of course). Set up your music app to play the same song on a loop. Make sure all volumes are down. Phone must be in mute. Turn of auto-brightness just in case. Morfic told me that to avoid the problem of the battery not reporting itself properly you can begin both tests with the same charging procedure: charge while off overnight. In the morning bump charge for exactly one hour. Disconnect, boot, start music immediately. Power button to screen off. Leave phone for 48 hours (should be enough time to auto power off).
After the first test, check the history from battery monitor widget to see how long the phone was on for.
Repeat again but with SOMF set to on.
***
Here's more on metering the amps:
REMEMBER I ADVISE THAT NO ONE SHOULD ATTEMPT THIS.
If you're thinking this is something you'd like to try, you'll need:
1) An analogue multimeter or pure ammeter because a digital one will be difficult to read with constantly changing amps.
2) Two battery caddies with space for 3 AA batteries each.
3) Six rechargeable batteries. Use rechargable ones because the volts are a bit less, 3*1.35=4.05 - close enough to the spec 3.7
4) Lots of cables with crocodile clip ends
5) Some fine copper wire
If you're thinking of soldering something onto your battery, DON'T - you may accidentally make a short circuit that will be difficult to undo, and cause the battery to explode. Plus the heat of the soldering iron certainly won't do it any good. And don't solder anything onto your phone contacts, just carefully twist a few strands of copper wire around them, so they can be easily removed. REMEMBER I ADVISE THAT NO ONE SHOULD ATTEMPT THIS.
[Q] Why do I need 6 AA batteries when 3 would provide enough volts?
[A] My multimeter inserts a 600 ohm resistor into the circuit (yours may be less, and if so you will need different calculations to convert to amps). This resistor allows the multimeter to evaluate the amps by measuring the voltage drop across it. But the resistance will cause your phone to starve of power. Running a parallel battery to the phone will prevent it crashing when the voltage supply isn't sufficient for things like screen on+cpu max frequency+sdcard IO... This parallel supply should run directly to the phone, not through the multimeter. It can be disconnected when the screen is off, and will not harm the phone. Remember to reattach it before powering on your screen, or it is likely your phone will crash. I would advise to start with fully recharged batteries, and not connect the USB charger.
[Q] Won't the amps read half of what is actually being drawn?
[A] Yes, but you'll get the correct reading if you unhook the parallel battery.
[Q] Might I also be able to do that when the screen is on?
[A] Yes, but I recommend that you do that with everything possible powered off, wifi, 3G... etc... screen brightness minimum. Set your screen timeout to never, so that you have control over it with the power button. Always reconnect your parallel battery before changing from screen on to screen off, and visa versa. (Due to large power spike)
[Q] I want to try this. Should I?
[A] No, no-one should try this.

Miscellaneous
[Q] You claim you cannot increase battery life using UV beyond 2%. Justify yourself!
[A] When the processor is in use (i.e. not asleep or idle) UV does save a tiny amount of power. I tested with the most extreme UV my phone could handle. With a high performance governor, e.g. smartassv2, extreme UV would reduce CPU drain by 13%, or about 7 mA. With a governor that keeps the CPU frequency low, CPU drain would be reduced by about 18%, or 4.6 mA (weighted - see the spreadsheet starting cell H88).
Remember, these savings are limited to the processor, and only when it is active. For most users, this will mean the screen is on. For comparison, the screen on minimum brightness displaying black uses 9mA. On max brightness, displaying white, it uses 690mA. Let us assume some median value, ~350 mA.
A saving of 4.6 mA out of at least 350 mA (screen) plus 20 mA (CPU)
= 1.2%
A saving of 7 mA out of at least 350 mA (screen) plus 50 mA (CPU)
= 1.8%
So, regardless of your choice of governor, even with extreme undervolting, you are not going to be able to increase your battery life by more than 2%.
Articles and Documents
Diane Hackborn's article on the formula that produces the dodgy Android OS usage statistic in the battery menu:
https://plus.google.com/105051985738280261832/posts/FV3LVtdVxPT
(note, this bug is fixed as of Android 4.0.4)
Data sheet for the fuel gauge chip:
http://www.maxim-ic.com/datasheet/index.mvp/id/6621
Link to great article on SOC (State of Charge) http://www.mpoweruk.com/soc.htm >>> explains all the reasons why I don't trust battery monitor widget and the phone's own battery stats.
Great article on the difficulties of accurate metering (thanks aLNG):
http://low-powerwireless.com/blog/d...t-schemes-for-battery-powered-devices-part-1/
In the article DUT stands for Device Under Test
The implication is that DMM [Digital Multi Meter] voltage drop readings (to measure amps) take hundreds of milliseconds, a will miss instantaneous battery savings above this time window. However, I am using an analogue meter, the the needle responds to all current. Due to the mass of the needle, there is inertia to overcome, which provides a form of averaging.
Quote from the article:
"a GSM cell phone can have current pulses of 2 amperes that last approximately 500μs while the power amplifier is on and transmitting, and then drop back down to the milliampere level for the remainder of the 4.5 ms GSM cycle."
500μs is 0.5ms, so is 1 tenth of the 5ms GSM cycle. 2 amps at 1/10th of 5ms = average of 200 mA
When I ran the test with my equipment, GSM broadcasting uses at least 170 mA - see row 36. I think this is a nice proof that the analogue multimeter beats the digital multimeter hands down for dynamic amps (i.e. changes happening below the millisecond level.) I'm also very satisfied that my result is close to the result stipulated by the article. It improves faith that my readings are accurate.
[Q] What could add inaccuracy to the readings?
[A] The dBm scale assumes a resistance of 600 ohms, but the resistor has 3% accuracy which means it could be as high as 618 ohms, or as low as 584 ohms.
[A] Also, the scale is very small, so I've read the needle to the nearest fifth of a dB
Other articles (thanks aLNG)
A study of the mA drain of various components of a smartphone
http://www.usenix.org/event/atc10/te...rs/Carroll.pdf
An ARM presentation on unifying power management procedures in the kernel
http://elinux.org/images/0/09/Elce11_pieralisi.pdf

UPDATE: Undervolting the CPU tested (using nstools ARM+INT)
UPDATE: impact of different screen colours tested (amoled)
UPDATE: Running apps tested.
Please note, the running apps draw power for lots of different reasons, access RAM, CPU, I/O, Graphics, all use power, what's being displayed also uses power, eg a brighter 3D scene vs a darker 3D scene. But it does give an overall idea of what Amps might be pulled when you are using the phone normally.

Thanks for your hard works I'm impressed with the systematic research.
Many things just the theoretical possibility? just something we created in our minds...

mobile_pc said:
Thanks for your hard works I'm impressed with the systematic research.
Many things just the theoretical possibility? just something we created in our minds...
Click to expand...
Click to collapse
Indeed, i agree. Now, with no benefit to under volting, perhaps we can all suffer less reboots.
For kernel benchmarks and more, see here: http://goo.gl/mpeHI

I have undervolted and overvolted in GB with direct impact on the battery life. The fact your undervolting tests show absolutely no difference in battery drain make me think the settings aren't even applied.
Also this part of your spreadsheet seems to be a bit lacking. What frequency voltages were changed? 100MHz? 200Mhz? All?
The smallest voltage I've seen stable for 100MHz ARM seems to be 825mv, for example.
Cheers

polobunny said:
I have undervolted and overvolted in GB with direct impact on the battery life. The fact your undervolting tests show absolutely no difference in battery drain make me think the settings aren't even applied.
Also this part of your spreadsheet seems to be a bit lacking. What frequency voltages were changed? 100MHz? 200Mhz? All?
The smallest voltage I've seen stable for 100MHz ARM seems to be 825mv, for example.
Cheers
Click to expand...
Click to collapse
The frequency information is there in the first column, eg 400/400 means the min and max settings were both 400. If you're not changing frequencies you can get it down very low.
Yes, perhaps nstools is defective. However, i did get an instant reboot with the lowest setting. Want me to do a repeat in GB?
For kernel benchmarks and more, see here: http://goo.gl/mpeHI

So undervolting does nothing? That seems strange ...
Also what about using juice defender? Worth it ?

italia0101 said:
So undervolting does nothing? That seems strange ...
Also what about using juice defender? Worth it ?
Click to expand...
Click to collapse
Yeah, does nothing to save battery. I don't know what juice defender is?
Sent from my SNES

polobunny said:
I have undervolted and overvolted in GB with direct impact on the battery life. The fact your undervolting tests show absolutely no difference in battery drain make me think the settings aren't even applied.
Also this part of your spreadsheet seems to be a bit lacking. What frequency voltages were changed? 100MHz? 200Mhz? All?
The smallest voltage I've seen stable for 100MHz ARM seems to be 825mv, for example.
Cheers
Click to expand...
Click to collapse
Okay, I went ahead and tested Gingerbread (carbon, ICS themed Oxygen 2.3.1, android 2.3.7) using franco's last kernel for GB. Starts at row 329.
Neither extreme undervolting nor overvolting had any impact on the battery drain.

Juice defender is a battery saving app that basically d/cs the data and wifi when screen is off and reconnects when screen is on... also when screen is off it uses schedules to turn wifi/data on to receive stuff and sync

italia0101 said:
Juice defender is a battery saving app that basically d/cs the data and wifi when screen is off and reconnects when screen is on... also when screen is off it uses schedules to turn wifi/data on to receive stuff and sync
Click to expand...
Click to collapse
Sounds sensible enough to me!
Sent from my SNES

Some reserves
bedalus said:
2 - If you use NStools to undervolt, don't bother. No gain to be had from undervolting either ARM or INT voltages. I tested this to the extreme. Check the spreadsheet, near the bottom. (Tested in both ICS and GB).
Click to expand...
Click to collapse
First, I want to thank you for all your efforts in the benchmarks especially for the battery drain. However, I kindly have some reserves on this. Maybe undervolting does not save so much power at idle but at higher loads, energy can be surely saved. Besides, maybe the energy saved is too minimal for your analog multimeter and it can't be noticed on it.
This is the theory :
The switching power dissipated by a chip using static CMOS gates is C·V2·f, where C is the capacitance being switched per clock cycle, V is voltage, and f is the switching frequency,[1] so this part of the power consumption decreases quadratically with voltage.
Click to expand...
Click to collapse
source : http://en.wikipedia.org/wiki/Dynamic_voltage_scaling
And this a more practical reference about a study made by tom's hardware on AMD Athlon clock, voltage and power consumption. I think it can be generalized (at a smaller scale) for our ARM processor in the nexus S:
It’s only when we change the voltage that we're able to significantly save more power--about 13 watts lower consumption, or a total of 20 watts compared to running without power management. That's a savings of 25%.
Click to expand...
Click to collapse
source (you may also read the entire article. It is very significant):
http://www.tomshardware.com/reviews/processor-power-management,2453-9.html
Other scientific papers and studies can be also found stating that undervolting saves power.
Kind regards.

I also appreciate all the hard work you have done for testing, on both kernels and everything, but im going to "gingerly" throw my hat in with tchaari here...
The only way to actually test battery drain would be to attach a multimeter and let it drain all the way on every test, using every kernel, and every setting - multiple times to omit false positives. Obviously this is beyond the acceptable timeframe it would actually take to accomplish. anyone would go insane sitting there waiting.
there are nuances here that will affect results regardless how carefull one is. the program itself might suck juice, your kernel/gov choice affects how the program runs too...also the status of your battery makes a difference. is it past it's half cycle life? etc..then the multimeter is another massive factor. there are many many different types not saying yours is bad, but over the years as an electrician ive played with some that are $20 as well as $2000 - and they are a far cry from each other even though they both do the exact same functions!
The undervoltage is a prime example. there are so many factors that will affect the results it's unusual to see your sheet having barely any differences - when we know that undervolting does actually save you battery under loads.
so it's nice to see a massive sheet like you did, as it does give a good start point reference - but it should be used not as chipped into stone law either.
Thanks for taking the time to give a great, no excellent base line to work off of though and preform more intense testing if people would like to go that far.

t3xboar said:
there are nuances here that will affect results regardless how carefull one is. the program itself might suck juice... then the multimeter is another massive factor. there are many many different types not saying yours is bad, but over the years as an electrician ive played with some that are $20 as well as $2000 - and they are a far cry from each other even though they both do the exact same functions!
Click to expand...
Click to collapse
What program? I'm playing a loop of silence in the music app to keep the processor awake.
The multimeter I'm using isn't fancy, but even if it's reading 10% down, it's doing it for all readings, so it's a fair comparison.
t3xboar said:
The undervoltage is a prime example. there are so many factors that will affect the results it's unusual to see your sheet having barely any differences - when we know that undervolting does actually save you battery under loads.
Click to expand...
Click to collapse
What makes you say we know this? I want to get to the bottom of this, so i need to see a concrete source.
Tchaari posted the capacitance times volts squared times frequency formula. I know this, and when I adjust the ARM voltage by more than half a volt, i expect to see this:
0.8x0.8=0.64
1.5x1.5=2.25
That should be 3.5 times as much power use.
Now, double the power in the dB scale is a difference of ~3dB. 3.5 times ~5dB. And I can notice a change of 1/5th of a dB on my multimeter's scale. There was no change. Here is how i tested.
Start music. Go into nstools, set ondemand with min and max at the same frequency. Go to volt, select the lowest possible voltage for that freq and exit. Screen off, measure amps. Screen on, nstools, volts, highest volts this time, exit, screen off, measure amps. Result: identical.
Seriously, if you have a background in electronics, have a go yourself (NO ONE SHOULD TRY THIS THEMSELVES) and get back to me.
In theory, it should save power, but it isn't. I'd love to be able to say why. At this point i don't think it's a problem with nstools, because i got a crash the second i put the volts to minimum when i was testing on Steve's kernel in ICS.
Sent from my SNES

As contradictory as some of these results may (or may not) be, bedalus is in the right with his methodology as far as i can see. Though at this point nothing should be set in stone. Not yet at least.

A few people saying with UV that they get more screen on hours, up from 3 to 6 hours. I'll check amps pulled (with both UV and OV) with screen on next.
Sent from my SNES

bedalus said:
A few people saying with UV that they get more screen on hours, up from 3 to 6 hours. I'll check amps pulled (with both UV and OV) with screen on next.
Click to expand...
Click to collapse
That is a good idea bedalus but it seems that undervolting gain is very minimal instantly. In a long period, it can make some difference in battery life...
I have also many doubts about how sensitive your amps-meter is? Since we are dealing with small values in our case, maybe a more sensitive device can measure some difference that yours can't...
Anyway, your work is very interesting and as Harbb said : At this point, nothing should be set in stone yet.

[Q] CPU Explanation

Hello, can someone please explain how my battery life improves when I set minimum cpu clock from 200 to 500?
I usually get 3 hours of screen time, with 500 as minimum I get nearly 4 hours. This difference is significant enough to make me wonder and ponder about how this happens.
It's counter logical, something with a higher minimum should drain faster.. right?

Does both cpu states are working at the same voltage? If yes (or the difference is very small) then the battery saving are from the increased execution speed .

In my own opinion, i dont think it affect much, while more than 70%+ battery drain by screen, unless u use cpu 100% all the time, otherwise i wouldnt too much concern abt that
Sent from my GT-N7000 using XDA Premium HD app

Chip efficiency changes with frequency. We tested this on my other phone (an Atrix- nice phone even now!)
Sometimes the CPU is just more power efficient doing tasks at higher frequencies. In a sense, the processor works faster, but for less time- so although it is running faster and requires more battery power, it completes the task much earlier and uses less power in total for that process.
My note, when running at 1.4ghz uses battery so much faster than at 1ghz, but the battery saving when dropping down from 1ghz is minimal, if existent at all.

Welcome to the not-always-intuitive world of modern CPU power usage.
The old mantra "higher frequencies use more power" becomes muddy in situations where the CPU can clock-gate parts of the chip when idle (cpuidle) and where the CPU voltage can change.
It was proven nearly a decade ago that if you don't change voltage at all with clock AND you have a good cpuidle implementation - it is actually best to always clock the CPU at maximum frequency. When voltage changes are in effect - it's harder to tell.
On most devices, the voltage for 500 and 200 are nearly identical. 500 does, I believe, have a somewhat higher bus frequency. So for a given workload, 500 MHz at, say, 20% load will use not much more power than 200 MHz at 50% load. In some cases, a device running at 500 MHz will finish a task more quickly and enter deep sleep faster.
Pretty much - 200 vs. 500 is really questionable in terms of which is best for power consumption. This is why I always set my screen-on minimum to 500.
Any frequency below 200 MHz is pointless as you can't undervolt those frequencies enough compared to 200 to make them have any benefit - in fact in many cases, adding a 100 MHz step is WORSE for battery.
Edit: One thing to note - In Gingerbread, the cpuidle driver was FAR less effective than it is in ICS. Only LPA and IDLE states were enabled by default, and the target residency for both was 40 ms.
In ICS, LPA, AFTR, and IDLE states are enabled and the target residency is 10ms. So it can hit deeper idle states far more often. For example, AFTR isn't as good as LPA - but it's better than dropping all the way to IDLE if you can't enter LPA. This is, in general, why the power consumption when wakelocked is much lower in ICS.
The bad news is that the suspend/resume cycle of the device is longer in ICS, AND cpuidle is totally blocked during suspend/resume - so the suspend/resume cycle eats even more juice than it did before, and it was historically one of the biggest users of power. Eventually I want to try and reduce this consumption.

Thanks for the good explanation mate, it has made things clear for me
Will be keeping my note on minimum of 500MHz aswell as it is a good improvement with no or next to no extra battery drain