Battery Life on a SmartPhone - The Riddle, The Enigma
I have been asked to port my original Battery Guide over to the SGS3 threads, so here it is in all it's glory.
This thread was also recently featured on the XDA Portal. Thanks to Haroon Q. Raja for the write up.
Attaining 20+ hours of battery life is not only possible it is totally attainable with most phone configurations. The secret to making this happen is, understanding what are the contributing factors are and knowing what to do first.
This guide will help. After reading this guide, you will be able to understand how to end power eating culprits and answer those same questions we see over and over in the threads...... that is .... solving the passive battery drain and get the 20 hours of battery life we all want and desire.
As we all know, all Samsung Galaxy S 3's and their Chipsets are not created equal. So if something works for one person and not the other, then is it a software, hardware or human error. Chances are it is a combination of all three. Hopefully this can slim those down a bit and answer some questions that you might have or have seen. I have tried to get almost everything I can think of and put it in one place.
You can click on the Post # below and it will take you directly to that post if you wanted to skip some things (although I don't know why you would want to do that)
Post 1: Tips and Tricks Post 2: Roms/Kernels, OverClocking/Undervolting, Governors & I/O Schedulers Post 3: Memory Management Post 4: Apps (for your download pleasure) Post 5: Proof
I will be using satirical stories and anecdotes to get my point across below. Not meant to offend or point fingers at anyone. I am just using real life references to get to the point. Also I am not much for fancy colors. I tried it at the top here but not so much further down. If there is something specific I want to call attention too, I will BOLD it and maybe RED it too.
This is not a GUIDE to get better battery life but rather a GUIDEline to get it. What is the difference, you say? A Guide is a step by step process that you must/should follow to get the outcome that the person who created it wanted you to get [A+B+C+D should = E]. A Guideline is more of a recommendation that allows some choice or flexibility in the understanding, execution or use [A +B-(C+D) can = E].
TopShelf10 has this to say about getting the most out of your battery life
the problem is, people want to believe that they can save battery without changing their usage habits. this simply is not possible. no rom or kernel will realistically do this for you. if you remove 1 brick from a bag full of 15 bricks, the bag will be lighter, but still very heavy. you need to download "spare parts" or "process monitor" from the market and start analyzing the way your apps are acting. also look into data syncs that are happening in the background. apps that stay open behind your back/what they are doing 9an app called "autostarts" can prevent apps from self-running under certain scenarios). animation speed. polling for notifications. gps. wifi scans. overclocking. cpu/ram usage. proper sleep. widgets. brightness. 2g/3g. data usage. call time. text volume. - THESE are the things that really affect your battery life.
bottom line is, if you truly want to save battery you are going to have to get your hands dirty...there simply isnt a one-click (or one-flash) solution.
Below is a list of fundamental things that can be done without rooting or custom ROM/Kernels. (Standard disclaimer applies: You use it, you set it and you are responsible)
1. Be Realistic -
Do you really think that you can get two whole days out of your battery? If you do, then you must have a very important pile of papers it is sitting on to not even pick up your phone for that long. These are phones. These are mini-computers. These are arcade games. And they want, dare I say, need to be played with, talked on or downloaded to. USE YOUR PHONE.
2. Syncing –
I know you are very important and you need to know what LeBron is doing right now, just in case you get a cup for a coffee and he might be in Starbucks at the same time and you get your picture taken with him and upload it to Facebook, Twitter or Google+. That is fine and I applaud you for it and will probably download the picture and Photoshop myself in your place. This is not the problem. Syncing your accounts is. That is what is causing battery drain. Do you really need to have your FB widget (see widgets section) streaming all day long? Does Kim K.’s endorsement of a potato chip really affect your everyday life? I doubt it. Kill them (not LeBron or Kim K. but rather the auto-syncing). Every time you “friend” someone their numbers, contact info gets sync’d to your phone. Also, there are settings in Facebook, Twitter and Google+ that you can upload pictures instantly. Don’t do that. Once you do, it is out in the Ether-World and just swallowed a bunch of battery doing it too.
Settings>Accounts and Sync>Auto-sync>uncheck it
3. Widgets –
They look cool. But widgets are nothing more than RAM and battery hungry monsters that you purposely put in your home screen. Think about it. What does a widget really do? All it really does is monitor an app that you have running. So not only is it running and taking up battery and RAM but the app that it is linked to is running in the background al’ a Facebook, Twitter, Google+, CNBC, MSNBC, BBC,… the list goes on and on because they want us to put THEM on our home page.
What a great marketing campaign the widget is.
“Hey look at me new home screen”
“Cool. Hey what widget is that?”
“Oh, it is X”
“Nice, I’ll have to download that tonight when I get home” and then and there they have you and your battery.
4. Apps – You have to pay attention to your apps. I repeat. You have to pay attention to your apps. Especially if they run in the background. This can be anything from a harmless .99c game to a monster like Live Wallpaper. The battery drain threat is twofold here because the app is running in the background but it could also be using its anonymous data collection abilities and sending that back to the Mothership. Ever wonder why you have a 4/3G with up and down arrows in your status bar when your phone is just sitting there? This is because some app is transmitting data, whether you are using it or not. There are apps in the market that monitor these situations like Watchdog or kill the data link when the lock screen is enabled like Juice Defender (see Apps below) or you can adjust app permissions like LBE Privacy Guard. Data transfer is #2 on the What Kills My Battery list.
#1 when it comes to what is eating your battery. Always has been and always will be. Accept it and try to do something about it. This part is easy. Just lower the brightness. You can use Auto or set it as a brightness that is low but you are still able to see well enough to function. Live Wallpapers fall into this category. They are cool to look at but static ones take up less RAM and also less display because they are not running all the time in the background. These screens are bright at 100%, so tone it down. (see Apps below).
Another helpful tip is setting your WIFI sleep policy to Always. This can be done by going here Setting>Wireless>WIFI> Menu key>Advanced>WIFI Sleep Policy and set it to Always.
--->Then you can also do this Build.Prop edit as well (this is if you are Rooted, of course)
Allows your wifi to scan less, saving more battery: wifi.supplicant_scan_interval=240 (I have mine set to 420)
Airplane Mode Toggle:
DocHoliday77 has this very helpful trick regarding Airplane Mode and how it effects your Data/Battery life.
I generally suggest toggling Airplane Mode on/off as a recommended step before running data speed tests, and to help with signal strength.
When you move from one area to another, generally your phone will automatically switch to another tower as the signal/connection to the current tower degrades. This is perfectly fine while travelling since you are not in a single location for very long. The problem comes into play once you have reached your destination. For many people, when they get home from work, for example, their phone will remain connected to the last tower they switched to on their drive home. However, there is very often a tower closer to their home that can provide better signal. The phone does not automatically switch to the better tower because it is still close enough to the current one to have adequate signal. By toggling Airplane Mode on/off, when the radio turns back on it will search for the strongest signal and will now connect to the closer, better tower!
Stronger signal will directly translate to a better battery. The better your signal, the less power is consumed for ALL radio operations (Including Cell Standby, Data, and Voice)! When the signal is weak, the radio requires more power to transmit to the receiver (the tower), which translates to higher battery use.
Toggle Airplane Mode on then off again to force the phone to connect to the best possible tower.
Animations: Set Settings > Display > Animations to .5 animations.
As pointed out by Arlanthir if your device is broadcasting your location, then you may need to rethink whether or not that is good for you and your battery. Generally, your location is based off GPS, Wifi or Mobile Networks. If these are on, then battery drain is occurring. Sometimes you need your location to work with Maps, Google Now, but most of the time, it is because of the unholy trinity, Facebook, Twitter and Google+. I mean, how do you think you "Check-In' at places right?
If you don't utilise these types of features on those three, then go into Settings>Location and untick them. Now there are also other apps like MLB At-Bat and the like that require location for blacked out games or services based on your location. I find that there is always a toast in those applications that notifies me and allows me to turn then on as needed. Then when I am done, I can turn them off.
These are 5 fundamental things that you can do to help reduce battery drain and get some more life out of your phone. Anyone can do these. All you have to do is watch your phone and use some common sense. “Why does my battery drain after only 6 hours? All I was doing was checking Facebook.” Do you really need to be on Facebook for that long of a time? I doubt it. How many services do you have running? How many tasks do you have running? (Android does a good job of shutting down tasks on its own, but if you are using a task killer, it takes more juice to start up an app than to turn it back on, so to say.) Think of it like an airplane. Takes more fuel to get up in the clouds, but once you are up there, it is pretty much coasting along with way less burn.
A special thanks to DocHoliday77 for convincing me to port this over and also for some of his helpful tips as well. You know who he is, so hit his thanks button to show your appreciation for all he does for this community.
ROMs are key things to think about when it comes to battery life. They can be fully established and working fine, can be RCs and still in development or they can be Alpha/Betas and completely experimental or just beginning. Choosing the best ROM or Kernel is going to depend on what YOU want out of your phone. Do you want a stable 4.0 ROM that has great battery life but not the customizability as MIUI or CM10 or AOKP? Because we have so many versions of 4.0.x ROMs that are official and almost all the sources have been attained, they have been Optimized to their fullest and some outstanding tweaks have really brought them to the forefront in daily drivers. Again, the choice is up to you.
Kernels go hand-in-hand with your ROM. Does the kernel support Overclocking or Undervolting. How much RAM and what tweaks are included in the kernel? Does THIS kernel work with THAT ROM? These are all spelled out for you in the OP of each kernel (and ROM) for you to find out. Read them because if you don’t, you’ll bork your phone and then your next post will be, “Help. I Bricked my phone”.
If you don’t already know what Overclocking is, well it is pretty much self-explanatory. You can Overclock your CPU above the clock-speed that Samsung, T-Mobile governed it at. This can be done with apps like SetCPU (here and here and CPUtuner,…Generally have to be ROOTed to do these but if you are flashing ROMs and Kernels then you probably already are. UnderVolting is basically what it sounds like too. You are Undervolting your CPU to conserve battery.
This can be one of the best ways for a more advanced user to save battery. Overclocking is great to see those really cool Quadrant scores. Wow!!! But it also ramps up the battery drain, as well as temperature which can shorten your battery’s TOTAL life. If you want to Overclock to 1.8-2.1 just to see what you score on Quadrant or SmartBench, then do it for that time. Most ROMs/Kernels run stable and smooth at or about 1.2-1.6 with minimal effects on battery (as long as you do tweaks in above post). If you decide to Undervolt you can use Pimp My CPU, Voltage Control, SetCPU,... to do this but take care to step it down slowly until you find the right settings for you or you will see random reboots or phone freezes and those suck trying to diagnose.
***Please note that whether you Overclock or Undervolt, do NOT “Set on Boot” until you know that they are going to work. Otherwise if it doesn’t work and your phone randomly reboots, you will get into a boot cycle (not a bootloop) because you put them in “Set on Boot”. You must test before you should do this.***
Example scale of OC/UV setting from Ktoonsez' thread:
Default governor in almost all stock kernels. One main goal of the ondemand governor is to switch to max frequency as soon as there is a CPU activity detected to ensure the responsiveness of the system. (You can change this behavior using smooth scaling parameters, refer Siyah tweaks at the end of 3rd post.) Effectively, it uses the CPU busy time as the answer to "how critical is performance right now" question. So Ondemand jumps to maximum frequency when CPU is busy and decreases the frequency gradually when CPU is less loaded/apporaching idle. Even though many of us consider this a reliable governor, it falls short on battery saving and performance on default settings. One potential reason for ondemand governor being not very power efficient is that the governor decide the next target frequency by instant requirement during sampling interval. The instant requirement can response quickly to workload change, but it does not usually reflect workload real CPU usage requirement in a small longer time and it possibly causes frequently change between highest and lowest frequency.
Basically an ondemand with suspend/wake profiles. This governor is supposed to be a battery friendly ondemand. When screen is off, max frequency is capped at 500 mhz. Even though ondemand is the default governor in many kernel and is considered safe/stable, the support for ondemand/ondemandX depends on CPU capability to do fast frequency switching which are very low latency frequency transitions. I have read somewhere that the performance of ondemand/ondemandx were significantly varying for different i/o schedulers. This is not true for most of the other governors. I personally feel ondemand/ondemandx goes best with SIO I/O scheduler.
A slower Ondemand which scales up slowly to save battery. The conservative governor is based on the ondemand governor. It functions like the Ondemand governor by dynamically adjusting frequencies based on processor utilization. However, the conservative governor increases and decreases CPU speed more gradually. Simply put, this governor increases the frequency step by step on CPU load and jumps to lowest frequency on CPU idle. Conservative governor aims to dynamically adjust the CPU frequency to current utilization, without jumping to max frequency. The sampling_down_factor value acts as a negative multiplier of sampling_rate to reduce the frequency that the scheduler samples the CPU utilization. For example, if sampling_rate equal to 20,000 and sampling_down_factor is 2, the governor samples the CPU utilization every 40,000 microseconds.
Can be considered a faster ondemand. So more snappier, less battery. Interactive is designed for latency-sensitive, interactive workloads. Instead of sampling at every interval like ondemand, it determines how to scale up when CPU comes out of idle. The governor has the following advantages: 1) More consistent ramping, because existing governors do their CPU load sampling in a workqueue context, but interactive governor does this in a timer context, which gives more consistent CPU load sampling. 2) Higher priority for CPU frequency increase, thus giving the remaining tasks the CPU performance benefit, unlike existing governors which schedule ramp-up work to occur after your performance starved tasks have completed. Interactive It's an intelligent Ondemand because of stability optimizations. Why??
Sampling the CPU load every X ms (like Ondemand) can lead to under-powering the CPU for X ms, leading to dropped frames, stuttering UI, etc. Instead of sampling the CPU at a specified rate, the interactive governor will check whether to scale the CPU frequency up soon after coming out of idle. When the CPU comes out of idle, a timer is configured to fire within 1-2 ticks. If the CPU is very busy between exiting idle and when the timer fires, then we assume the CPU is underpowered and ramp to max frequency.
This is an Interactive governor with a wake profile. More battery friendly than interactive.
This new find from Tegrak is based on Interactive & Smartass governors and is one of the favorites. Old Version: When workload is greater than or equal to 60%, the governor scales up CPU to next higher step. When workload is less than 60%, governor scales down CPU to next lower step. When screen is off, frequency is locked to global scaling minimum frequency. New Version: Three more user configurable parameters: inc_cpu_load, pump_up_step, pump_down_step. Unlike older version, this one gives more control for the user. We can set the threshold at which governor decides to scale up/down. We can also set number of frequency steps to be skipped while polling up and down.
When workload greater than or equal to inc_cpu_load, governor scales CPU pump_up_step steps up. When workload is less than inc_cpu_load, governor scales CPU down pump_down_step steps down.
If current frequency=200, Every up_sampling_time Us if cpu load >= 70%, cpu is scaled up 2 steps - to 800.
If current frequency =1200, Every down_sampling_time Us if cpu load < 70%, cpu is scaled down 1 step - to 1000.
Lulzactiveq is a modified lulzactive governor authored by XDA member robertobsc and is adapted in Siyah kernel for GS2 and GS3. Lulzactiveq aims to optimize the second version of luzactive from Tegrak by a) providing an extra parameter (dec_cpu_load) to make scaling down more sensible, and b) incorporating hotplug logic to the governor. Luzactiveq is the first ever interactive based governor with hotplugging logic inbuilt (atleast the first of its kind for the exynos platform). When CPU comes out of idle loop and it's time to make a scaling decision, if load >= inc_cpu_load CPU is scaled up (like original luzactiveq) and if load <dec_cpu_load, CPU is scaled down. This possibly eliminates the strict single cut-off frequency for luzactiveq to make CPU scaling decisions. Also, stand hotplug logic runs as a separate thread with the governor so that external hotplugging logic is not required to control hotplug in and out (turn On and Off) CPU cores in multi core devices like GS2 or GS3. Only a multi core aware governor makes real sense on muti-core devices. Lulzactiveq and pegasusq aims to do that.
Result of Erasmux rewriting the complete code of interactive governor. Main goal is to optimize battery life without comprising performance. Still, not as battery friendly as smartassV2 since screen-on minimum frequency is greater than frequencies used during screen-off. Smartass would jump up to highest frequency too often as well.
Version 2 of the original smartass governor from Erasmux. Another favorite for many a people. The governor aim for an "ideal frequency", and ramp up more aggressively towards this freq and less aggressive after. It uses different ideal frequencies for screen on and screen off, namely awake_ideal_freq and sleep_ideal_freq. This governor scales down CPU very fast (to hit sleep_ideal_freq soon) while screen is off and scales up rapidly to awake_ideal_freq (500 mhz for GS2 by default) when screen is on. There's no upper limit for frequency while screen is off (unlike Smartass). So the entire frequency range is available for the governor to use during screen-on and screen-off state. The motto of this governor is a balance between performance and battery.
Intellidemand aka Intelligent Ondemand from Faux is yet another governor that's based on ondemand. Unlike what some users believe, this governor is not the replacement for OC Daemon (Having different governors for sleep and awake). The original intellidemand behaves differently according to GPU usage. When GPU is really busy (gaming, maps, benchmarking, etc) intellidemand behaves like ondemand. When GPU is 'idling' (or moderately busy), intellidemand limits max frequency to a step depending on frequencies available in your device/kernel for saving battery. This is called browsing mode. We can see some 'traces' of interactive governor here. Frequency scale-up decision is made based on idling time of CPU. Lower idling time (<20%) causes CPU to scale-up from current frequency. Frequency scale-down happens at steps=5% of max frequency. (This parameter is tunable only in conservative, among the popular governors )
To sum up, this is an intelligent ondemand that enters browsing mode to limit max frequency when GPU is idling, and (exits browsing mode) behaves like ondemand when GPU is busy; to deliver performance for gaming and such. Intellidemand does not jump to highest frequency when screen is off.
This governor from Ezekeel is basically an ondemand with an additional parameter min_time_state to specify the minimum time CPU stays on a frequency before scaling up/down. The Idea here is to eliminate any instabilities caused by fast frequency switching by ondemand. Lazy governor polls more often than ondemand, but changes frequency only after completing min_time_state on a step overriding sampling interval. Lazy also has a screenoff_maxfreq parameter which when enabled will cause the governor to always select the maximum frequency while the screen is off.
Lagfree is similar to ondemand. Main difference is it's optimization to become more battery friendly. Frequency is gracefully decreased and increased, unlike ondemand which jumps to 100% too often. Lagfree does not skip any frequency step while scaling up or down. Remember that if there's a requirement for sudden burst of power, lagfree can not satisfy that since it has to raise cpu through each higher frequency step from current. Some users report that video playback using lagfree stutters a little.
Lionheart is a conservative-based governor which is based on samsung's update3 source. Tweaks comes from 1) Knzo 2) Morfic. The original idea comes from Netarchy. See here. The tunables (such as the thresholds and sampling rate) were changed so the governor behaves more like the performance one, at the cost of battery as the scaling is very aggressive.
To 'experience' Lionheart using conservative, try these tweaks:
sampling_rate:10000 or 20000 or 50000, whichever you feel is safer. (transition latency of the CPU is something below 10ms/10,000uS hence using 10,000 might not be safe).
Lionheart goes well with deadline i/o scheduler. When it comes to smoothness (not considering battery drain), a tuned conservative delivers more as compared to a tuned ondemand.
LionheartX is based on Lionheart but has a few changes on the tunables and features a suspend profile based on Smartass governor.
Similar to smartassV2. More aggressive ramping, so more performance, less battery.
Another smartassV2 based governor. Achieves good balance between performance & battery as compared to brazilianwax.
Instead of automatically determining frequencies, lets user set frequencies.
Locks max frequency to min frequency. Can not be used as a screen-on or even screen-off (if scaling min frequency is too low).
Sets min frequency as max frequency. Use this while benchmarking!
So, Governors can be categorized into 3/4 on a high level:
1.a) Ondemand Based:
Works on "ramp-up on high load" principle. CPU busy-time is taken into consideration for scaling decisions. Members: Ondemand, OndemandX, Intellidemand, Lazy, Lagfree.
1.b) Conservative Based:
Members: Conservative, Lionheart, LionheartX
2) Interactive Based:
Works on "make scaling decision when CPU comes out of idle-loop" principle. Members: Interactive, InteractiveX, Lulzactive, Luzactiveq, Smartass, SmartassV2, Brazilianwax, SavagedZen.
3) Weird Category:
Members: Userspace, Powersave, Performance.
Inserts all the incoming I/O requests to a First In First Out queue and implements request merging. Best used with storage devices that does not depend on mechanical movement to access data (yes, like our flash drives). Advantage here is that flash drives does not require reordering of multiple I/O requests unlike in normal hard drives.
Serves I/O requests with least number of cpu cycles. (Battery friendly?)
Best for flash drives since there is no seeking penalty.
Good throughput on db systems.
Reduction in number of cpu cycles used is proportional to drop in performance.
Goal is to minimize I/O latency or starvation of a request. The same is achieved by round robin policy to be fair among multiple I/O requests. Five queues are aggressively used to reorder incoming requests.
Nearly a real time scheduler.
Excels in reducing latency of any given single I/O.
Best scheduler for database access and queries.
Bandwidth requirement of a process - what percentage of CPU it needs, is easily calculated.
Like noop, a good scheduler for solid state/flash drives.
When system is overloaded, set of processes that may miss deadline is largely unpredictable.
Completely Fair Queuing scheduler maintains a scalable per-process I/O queue and attempts to distribute the available I/O bandwidth equally among all I/O requests. Each per-process queue contains synchronous requests from processes. Time slice allocated for each queue depends on the priority of the 'parent' process. V2 of CFQ has some fixes which solves process' i/o starvation and some small backward seeks in the hope of improving responsiveness.
Considered to deliver a balanced i/o performance.
Easiest to tune.
Excels on multiprocessor systems.
Best database system performance after deadline.
Some users report media scanning takes longest to complete using CFQ. This could be because of the property that since the bandwidth is equally distributed to all i/o operations during boot-up, media scanning is not given any special priority.
Jitter (worst-case-delay) exhibited can sometimes be high, because of the number of tasks competing for the disk.
Instead of time slices allocation by CFQ, BFQ assigns budgets. Disk is granted to an active process until it's budget (number of sectors) expires. BFQ assigns high budgets to non-read tasks. Budget assigned to a process varies over time as a function of it's behavior.
Believed to be very good for usb data transfer rate.
Believed to be the best scheduler for HD video recording and video streaming. (because of less jitter as compared to CFQ and others)
Considered an accurate i/o scheduler.
Achieves about 30% more throughput than CFQ on most workloads.
Not the best scheduler for benchmarking.
Higher budget assigned to a process can affect interactivity and increased latency.
Simple I/O scheduler aims to keep minimum overhead to achieve low latency to serve I/O requests. No priority quesues concepts, but only basic merging. Sio is a mix between noop & deadline. No reordering or sorting of requests.
Simple, so reliable.
Minimized starvation of requests.
Slow random-read speeds on flash drives, compared to other schedulers.
Sequential-read speeds on flash drives also not so good.
Unlike other schedulers, synchronous and asynchronous requests are not treated separately, instead a deadline is imposed for fairness. The next request to be served is based on it's distance from last request.
May be best for benchmarking because at the peak of it's 'form' VR performs best.
Performance fluctuation results in below-average performance at times.
Least reliable/most unstable.
Based on two facts
i) Disk seeks are really slow.
ii) Write operations can happen whenever, but there is always some process waiting for read operation.
So anticipatory prioritize read operations over write. It anticipates synchronous read operations.
Read requests from processes are never starved.
As good as noop for read-performance on flash drives.
'Guess works' might not be always reliable.
Reduced write-performance on high performance disks.
Some Kernel Settings from Users out "there" (Note: These are for the SGS3 kernels):
With my new settings I can get up to 5-6 hour of screen on with a discharging time of around 24 hours. Before I start playing with cpu1, I couldn't get more than 4hours of screen on with a discharging time around 15hours since the Linux 3.4 kernel
Note that I also use greening to hibernate apps and Tasker to turn on things like gps, data, wifi, auto rotate only when I need them.
I readjusted my settings yesterday to test something out if you got no loss in performance yet you can try them out:
Ktoonservative setup to input in ktweaker:
Boost 2nd core on button:0
Boost gpu: doesn't matter
Boost hold cycle :0
Boost turn on 2nd core:0
Cpu down block cycle:0
Down threshold hotplug:60
Ignore nice load:0
No 2nd cpu screen off:1
Sampling down factor:3
Sampling rate: 25000
Sampling rate screen off: 45000
Up threshold hotplug:96
If you set your ktoonservative to turn off 2nd core(cpu1) when screen is off, then it doesn't matter because your cpu1.will be off so only your ktoonservative(cpu0) settings matter. Personally I use 486 as my max freq when screen is off.
This is long INFO post from real chip designer that help to create CPU/GPU and other chips for the living for 14 years now, so respect
He sent me PM, for now he cant post that by him self.
Vikas is monitoring our thread and want to say his professional stand about UV/OV and why it's works for some and why not for others.
I am calling Vikas(vikas.mishra) to the speech stand
Let me introduce myself - my name is Vikas Mishra and I am a chip designer by profession. .
I have worked on critical parts of design of TI OMAP4, OMAP5, Nvidia Tegra 3 etc and have been doing this for the last 14 years.
Of late - I have seen a lot of folks posting BUGS about undervolting of the GPU/CPU.
I think I can explain what are the possible issues with undervolting/overclocking in a laymans language.
It is a little long winded but I think the length is needed for providing the appropriate context.
* What is inside your Cellphone
Your cellphone is an amazing device. It is a full fledged computer
that fits into your pocket. They have all the standard components
that a computer has - except that they are all usually soldered on
the motherboard directly and are not meant to be user-servicable.
The chief components inside your cellphone are
1. Application Processor (AP)- this is the heart of a modern
cellphone. These are manufactured by many companies - the main
ones are Qualcomm, Nvidia, Samsung and Apple. The other not so
well known ones are made by Texas Instruments, ST Ericsson,
Marvell and Broadcom.
A modern AP has logic to control the camera and process the image
that it generates, to do video encoding (video recording) and
video decoding (movie watching), Audio processor etc. in addition
to the well known CPU and GPU.
2. Power Management Controller - This is the chip that is
responsible for generating and regulating the voltages that are
used by all the components on the board.
3. DRAM - not very different from the DRAM found on a PC (except
that it is lower voltage)
4. Flash - for storage
5. Touchscreen controller
6. Logic for microphone, speaker
One of the most complex piece of circuitry on the phone is the AP
and the power management controller.
* Circuit Basics
A modern AP has millions of circuit units called (Flip
Flops). These flip flops have two parameters associated with them
called Setup time and Hold time. More details on what a flip flop
can be found on the wikipedia at http://en.wikipedia.org/wiki/Flip-flop_(electronics) . This is a
nice bit of bedside reading if you are interested.
A setup time roughly indicates what frequency you can run a design
or an AP at before it becomes unstable.
A hold time roughly indicates the maximum voltage till which a
design is stable.
A fully technical analysis of what is involved in these timing
parameters requires a degree in electrical engineering but in broad
terms the problem is described below.
Chip designers diligently ensure that all of the millions of the
flip flops in a chip meet the setup and hold time across a broad
range of voltages and silicon parameters. They do a pessimistic
analysis to ensure that a chip will run reliably across a wide
range of voltage/frequency combinations.
However, contrary to the popular belief, chips vary widely in their
silicon parameters. Even chips on a the same wafer and different
flip-flops within the same chip can have widely different silicon
parameters. This is why what works on one particular chip will not
work on the other chip.
Your silicon manufacturer provides a range of voltages and
frequencies across which the device can work reliably. The phone
manufacturer will further narrow down the range depending on the
other components they choose within the phone board.
* How does voltage affect the design
Reducing voltage makes the design slower and increasing voltage
makes the design faster.
So can I keep on increasing the voltage for ever and make the
circuit faster and faster. The answer is no - a point will come when
the circuit will become unreliable. This becomes unreliable because
the "hold time" of one or more of the flops will start
As you reduce the voltage of the design, the circuit will start
becoming slower. However typically it will continue to work till at
apoint it starts failing - this failure occurs due to violation of
"setup time" of one or more flops in the design.
So what happens when the setup time or the hold time of a design
fails - the answer is that it is unpredictable. Meaning suddenly if
you ask the processor what is the value of 2+2, the answer it will
provide could be unreliable - in some cases it could be 3, in some
cases it could be 4 in some cases it could be -2349783297 (a random number).
I am of course oversimplifying but I hope you get the picture.
* How does undervolting affect your phone processor
The reason undervolting is so appealing to people because they
thing that undervolting will save power and improve battery
life. While this is true in theory, in practice there is a caveat.
It will reduce the power of the chip, but the power consumed by the
phone as a whole will not improve. In some cases in fact it can
deteriorate. Let me explain.
The most power hungry part in the phone is not the AP - it is the
LCD screen. All of these screens consume a ton of power. So even
though your AP is now consuming lesser power, the overall impact to
the phone as a whole is not that much.
If you accompany undervolting with a frequency reduction (which you
should), the total time taken for doing a web page rendering (for
example) would increase. During this time the screen is on and it
has more than compensated for the power that you saved in the
You could of course come up with examples where this wouldn't
happen - but on a whole, IMHO, you should leave the voltage of the
AP/GPU/CPU to the guys who know the system best - the guys who
designed the chip and people who manufactured it.
* How does overvolting/overclocking affect your phone processor
If you want that last drop of performance from your phone and you
over clock it, at a point some of the design flops will start
violating the hold time and the design will stop working reliably.
Again, in some anecdotal cases this would work - but this is not a
reliable means/mode of working. Just because your friend's or your
first cousin's girlfriend's phone works - doesn't mean yours will
work as well.
* What are the user observable impacts of undervolting/overclocking?
It is hard to say - simply because there are so many of flops in
In some cases - you wouldn't see anything wrong with the phone
until one day you do. In some cases it will result in a SOD
immediately. In some cases it will result in your phone not waking
IMHO the risks of issues with undervolting/overclocking far
outweighthe potential gains you may get out of it. Usually there
is no lasting damage to the phone/AP if you overlock/undervolt but
it is possible to do it. For example, You run the phone at such a
high frequency that the chip temperature becomes more than what it
was designed for and the Silicon just fails.
So "Just say No" . Don't overclock or undervolt your phone -
leave it to the guys who really understand what they are doing.
Did you know that you can also free up some internal memory space by just basic maintenance? You can install a Cache Cleaner from the market. I use Cache Cleaner NG (root) and CacheMate (root) which will clear your cache for you, Cache Cleaner NG will even clear your cache on your SDcard. Open Root Explorer and if you see a bunch of free floating cache files, those need to go. Wasted space. Small in the scheme of your SDcard, but still wasted.
So here we go (best part is at the bottom though):
Ok so you go into XDA on your phone, go to the themes page and look at what and how people are theming their phones or see some pix of someone's SetCPU profiles. All those develop a cache that takes up space on your phone. Now lets say that you go to the market and look through some apps or update your apps (more on this later). This also generates cache, usually up to 2-4mb. Ever try to download something from the market and it says something like "not enough space". This not needed cache may be some of the reason.
Here are some tricks and apps that some of you may know and also some tricks that I have found that I am sure most don't know about.
Diskusage (free) ~ This one will show you a graphical version of your /data/apps and also you SD card to show you exactly what is taking up so much space. You can click on that item and hit "Show" and it will take you to the app's page in Manager Applications. It also has a root function too that will allow you to see what is in /system, /cache, /data,…
Some sort of file manager to get to some things I'll mention below. (I use Root Explorer)
SOME MEMORY CLEARING TIPS AND TRICKS:
Home Launcher ~ If you have a 3rd party home launcher, see if it has the ability to long-press an icon to take you to its screen in the Manage Apps section. I use APEX and if you long-press on say Market, it takes me to the same place as is I were to go to Settings->Applications->Manage Apps->Market. Instead of all that, just long-press on the icon and BAM! it takes you there. Here you can clear out your cache for the market or delete the data (if you need to do that). Or clear the cache of the XDA app b/c you looked at too many pix.
Browsers ~ These develop cache that takes up memory and space, especially the stock browser. If you use a 3rd party, you can get the settings to clear cache, cookies, passwords,…on exit. I use Dolphin, but I am pretty sure that most have something like this on them. (side note: most 3rd party browsers once exited will not run in the background unlike the stock one)
Media ~ So you download a bunch of mp3's from the net or click on some pix and save it to your SD card. Or maybe you just felt like wiping your card and having a fresh start. Every time you reboot, you phone will scan media. No big deal, but the more you criss-cross things from PC to phone and back again, it can create a bunch of double files in your media cache on the phone. With the proper placement of .nomedia files (this prevents your media scanner from doing just that, scanning media- i.e. pix, jpegs,…Don’t place a .nomedia in your music, album art or DCIM files**bad).
Every once in a while, I'll hit the Diskusage or go to Manage apps and clear the media cache. Then I got to my file manager and the DCIM->Thumbs and delete the .Thumbnails files (should be 2). Unmount the SD card and remount to start the media scan, pull up the Gallery and wait for the thumbs to come back (depending on how many you have, this could take awhile). By doing this you can get almost 5 mb back if you have a bunch of double scans in your media folder.
AND NOW FOR SOME TIPS THAT MOST COULD NOT KNOW:
LOSTDIR - Lets say that you have your phone plugged into your PC and for some reason you, in a fit of rage, jerk the plug out without unmounting it first. This creates a file that is put into your LOST DIR folder on your SD card. Anytime you don't safely unmount the SD card, it will create a file in that folder. In the scheme of the SD card, it isn't too much, but I don't like having useless items free floating about. Here is a good explanation of what the Lost.dir is for, seems legit, I buy it.
TOMBSTONES - So you are downloading an update from the market and for some reason your phone freezes and the Force Close-Retry-Wait doesn't work out for you. You have to do a battery pull. Frustrating I know and the memory takes a hit too. Every time you have to do a battery pull because of a freeze up or something of the like, it creates a TOMBSTONE file in /data. These are useless and can be deleted. If you are flashing ROMs and are constantly having to do battery pulls b/c market crashes or an app freezes, then you are creating a Tombstone file.
**Here is where your file manager (with root) will help. Go into /data and scroll all the way to the bottom and open /tombstone. There should be some files in there and depending on how many there are, I could be a nice chunk of wasted memory. Just select all and delete. They are not needed. Your internal memory should go up by doing this.
LOST & FOUND - Same scenario, but now go into /data/ cache or /cache and you'll see Dalvik-Cache (don’t mess with this), Lost & Found and Recovery. If you tried to download an app and it got frozen for some reason and had to do a battery pull, the apk will be free floating in there, uninstalled (free floating radical). You can delete this. While it isn't in the Dalvik-Cache folder, it is taking up space. Once you are able to download something completely and correctly from the market, it will populate into Dalvik-Cache correctly and won't be a free radical, as I like to say.
These are some apps that will help you get the most of your battery life. I will put a brief descpition of them and you can also click on their names to take you directly to their market link. Note that some of these are ROOT apps and almost all of them also have PAID versions that greatly expand their functionality. Use the free ones and see how you like them and then kick in for the PAID ones if you want. The only one that I really suggest paying for right out of the gate to get the most out of your battery is Juice Defender Plus.
Paid app from the Market. This app is highly technical and not for noobs. Use at your own risk.
I would love for some of you out there to give me your Tasker Battery Saving Profiles. Either put them in the thread here or PM to me directly.
This app is probably one of the best battery saving apps that has come out in quite a long time. It allows you to "Hibernate" apps that are not being used at the time, get them out of the foreground and prevents them from running when not in use, thus eating battery.
It is really easy to use. All you have to do is fire it up, grant Root and then select the apps that you want to "Hibernate". (Note: be very careful what types of apps that you do this with, i.e. /system/apps, as it could cause adverse effects like missed notifications, missed SMS/MMS, misbehaving apps,...you get my point I hope).
I know, I know. Above I said that widgets were nothing more that monitoring apps on your home page, but this one works great, has low memory and is very, very simple. It shows Charge in %, Volts to know when you are FULLY charged and Temperature F/C to tell you that your phone is getting hot and exactly how hot it is.
This app will show you what exactly is eating at your battery. Processes, Running Services, Wakelocks, Partial Wakelocks. It is a PAID app but for XDA users it is free. See here for more extensive details, instructions, screenies, change-logs,... and credits go to Chamonix and his development team for this app.
JuiceDefender (Plus) [Since I use JD+, that is what I am going to refer too.]
This apps ability to kill Radio/Data has NO EFFECT on phone calls or messaging. You will still get that call in the middle of the night you were expecting.
If you set it to custom, the go into the settings tab on the right and then all the way at the bottom, there is two buttons to push, The first in Interactive which will pull up Juice Defender for up for any app that isn't already configured and the other is Configure Apps. This is the one that you can customize on an app-to-app basis where if you are no using an app and the screen is locked, it kills the radio/data traffic for that app.
Say you are listening to IHeartRadio, this you would want either Enable or Enable/off (which means the screen will be locked but the radio/data will be working). Now take the browser. If you are not using the browser, then you don't need it transmitting data right? So you would set that one to Enable (which means that it will only enable data traffic when that app is being used).
Juice Defender only works when the screen is locked (WidgetLocker lock screens interfere with JuiceDefender), don't forget and all widgets are battery drains b/c all they really are is a monitoring app and if it is tied to something like Facebook or Google+, then that data will be running constantly.
Enable = Radio/data on when app is in use (front) Enable/off = Radio/data on for background apps (when screen is locked) Disable = Disables radio/data traffic completely when that app is running Do Nothing = What is says
Angry Birds = Disable (Here is a little known trick that I use for this and any game with Ads. With this and something like Adfree, no more ads in Angry Birds even though the ads are embedded in the .apk)
Pandora/Jango/ Tune-in = Enable/Off (this will keep your battery temp down when streaming)
Browser/ Market = Enable (not enable/off b/c then it will keep your radio/data open)
Beautiful Widgets = Enable/off
mClock/Clockr = Enable/off
SMS/MMS = Enable or Do Nothing (why would you push disable)
I have been using JD+ for over a year on 3 different phones and multiple ROMs and have noticed a considerable difference in battery life. Just takes some time to figure out YOUR settings and what YOU like. I have also used it on Stock kernel and had no problems either.
Here are my personal setting but I am on JD+ and not Ultimate
Profile - Customize
Notification - Graphical
Mobile Data and WIFI both Enable
Options - Auto Disable
Location - Disable
Schedule -Enable --->2hrs
Night Enable --->12a to 9a (user take priority)
Apps --.Set to Interactive
E = Enable
ESo = Enable/Scrren Off
D = Disable
DN = Do Nothing
At-Bat12 = ESo
IHeartRadio = ESo
Jango = ESo
Sticher = ESo
Dolphin = E
Google Play Store = E
Messaging = E
Twitter = E
XDA pre = E
Zedge = E
Angry Birds (all variants) = Disable --->You get no ads this way wink wink
These are all Do Nothing
PowerAmp -->I can listen to music without it looking for Album Art b/c it is set to do nothing, so one of the above apps take priority and when the screen is off, data is off when I am listening to music
Blah, blah, blah you get the idea.
If you have every app you own and in the phone set to do "something", then you are going to run into priority issues when multi-tasking which will kill your battery for 1 b/c it is opening and closing radios and 2 for the RAM it is taking to figure out which priority take the lead. Hence why I have so many set to Do Nothing.
LBE Privacy Guard
There may or may not be some issues with this app and Jelly Bean, so make sure you read the Market Comments and hit their website to make sure. Thanks to mypenismighty for the tip.
This will go good with JuiceDefender, as they both prevent unwanted data transfer. Protect your privacy by controlling the permission of each application to access your sensitive data. Block malicious operation from Mal-wares and Trojans. Block unwanted network traffic if you dont have a unlimited data plan. Find out which application is trying to steal your privacy by checking the security log.
RAM Munchers eat battery too. These will fix that for you.
This is a handy little app that kills all your services at once and lets them restart back up. I use this right before I hit the lock screen, so that if any app-services are running that I dont have configured in Juice Defender Plus they will be killed, frees up about 50-70mb of memory, and then I lock the screen and JD takes over. This one is optional if you want it or not. I like it just fine and it works for me. Matte Screen Filter
Puts a sort of Dim setting on your screen. Almost like a display overlay, ok? And I did mean to rhyme those. I dont use it because I have my display set how I want it but you can.
Battery Calibrator Pointless, but if you want to check out more info, click the hide tag below.
If you are having some haywire battery readings, this is for you. THIS WILL NOT INCREASE YOUR BATTERY LIFE, but will give you a truer reading if your battstats somehow get corrupted.
When you flash a new ROM, it is always best to wipe the old battery stats associated with that ROM, so you can start fresh as a daisy. How this works is you plug you phone in and charge to 100%, do not mess with it or surf the net (I do this overnight). While still plugged in, hit the apps, grant SU permission and hit the Calibrate Battery button. Grant SU permission again and once done, unplug your phone. Your Batterystats.bin has been deleted. You running your phone down by just using it normally. Most say to run it until it shuts off, but I have had bad experiences doing this, so I let it get to 10-15% and plug it in then. Charge fully up to 100% (again no surfing or games) and you will notice a dramatic increase in battery life.
**Note that this can be done two other ways. You can boot into CWR or Custom Recovery and go to Advanced Settings and there will be the Wipe Batterystats.bin option. Or you can do it manually by going into /data/system/ and deleting the batterystats.bin in there. Any of the three methods work to get the entirely same result in the end. I just like using the app or manually myself. **
Why battery calibration is important and what it is doing.
The app and what it does is more for when you are flashing a ROM and have around 60% and then once booted up fully, you charge it up to 100%. Decided you don't like your ROM and go back to your original ROM via backup, it will show 60% instead of the 100 or 90% you had before you went back to back up b/c you backed up the batstat bin when you nandroided your original ROM. Also simply charing your phone up to 100% and shortly after you unplug it, the Battstats will reset.
Recently (about this time last year) there has been information debunking this process. I will post it below. Here is the post by Dianne Hackborn, a Google Dev on her G+ account.
Dianne Hackborn - Jan 12, 2012 - Public
Today's myth debunking:
"The battery indicator in the status/notification bar is a reflection of the batterystats.bin file in the data/system/ directory."
No, it does not.
This file is used to maintain, across reboots, low-level data about the kinds of operations the device and your apps are doing between battery changes. That is, it is solely used to compute the blame for battery usage shown in the "Battery Use" UI in settings.
That is, it has deeply significant things like "app X held a wake lock for 2 minutes" and "the screen was on at 60% brightness for 10 minutes."
It has no impact on the current battery level shown to you.
It has no impact on your battery life.
Deleting it is not going to do anything to make your more device more fantastic and wonderful... well, unless you have some deep hatred for seeing anything shown in the battery usage UI. And anyway, it is reset every time you unplug from power with a relatively full charge (thus why the battery usage UI data resets at that point), so this would be a much easier way to make it go away.
Here is a post from this thread with ERD Entropy512 and I discussing the Battery Calibration app.
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