Hi,
I have a quite naive, ambicious and just theoretical question. HTC HD has a thermometer on CPU as probably most of todays PDAs. But, wouldn't be possible to count the temperature in the room(or wherever you are) due to the informations from this thermometer? Of course you would have to count a bit with the current performance of CPU(find out how much the CPU temperature affects data going out of the thermometer. But maybe after some mathematical operation it could work. I know it is very naive questin, but I just wanted to ask.
So thanks for the response
Nice idea, but cant see how this could work accurately as the variable (cpu/battery temp) various wildly depending on how heavily you are using it.
Be better (and more accurate) to rely on the weather app/msn weather widget for the external temperature.
Saying that, a developer might like the challenge
the thermometer is build into the cpu chip itself
and cpu usage have a much bigger impact on the temp
then area temp does
more so when these devices don't have big air grills for air circulation
so doubt it would ever work well as a room temp measuring device
I realize it would be complicated if not impossible .. but it was just an idea so I put it here.
Shooter92 said:
I realize it would be complicated if not impossible .. but it was just an idea so I put it here.
Click to expand...
Click to collapse
Actualy it was an application like that, it was for smartphones running wm2003, it wasn't so accurate.I was lookinking for something like this on the net but nothing found for pocket pc
Theoretically, a program could measure the temperature of the device overtime, taking the cpu usage, battery drainage, etc. to determine an equation to use in calculating the only missing variable: the outside temp. The equation could mathematically deduce that based on a given temperature with given variables (cpu usage, battery heat based on drainage, etc.).
However, the program would reasonably need to be device specific. Otherwise, small changes in hardware would change the results dramatically. Of course, the program could determine that, as I mentioned above, but it would introduce an entirely new set of variables and would probably need to run for a given time to sample the device (at least a week). It still may not even be possible that way because the device would not be able to reach the maximums and minimums of each variable...still, math could theoretically fill in the gaps.
That being said, it still would not be very accurate because there is actually 2 blank variables. If the temperature surrounding the phone was static (the same all the time) then this would work. BUT since you will be changing air temps quite frequently, the air temp would not have time to affect the device. It would be a slow increase or decrease until it finally levels out. Its like taking water and putting it in a freezer. It won't freeze immediately, but it will freeze over the course of several hours. You can be outside in 90 degree weather for several hours then walk back inside to 70 degree air. Your phone would still calculate the air temp as some where around 90 for quite a while.
Does that make sense?
Introduction:
If you’re reading this, I’m going to assume that you want to learn something new. I love sharing knowledge with others, so I hope you do as well. With that being said, please understand that I’m doing this in my spare time, and have no degree of any kind on this topic. What I’ve compiled here is a pretty good guide to explain and hopefully educate some of you on a highly talked about, but widely misunderstood concept of CPU architecture.
Before we begin, I need to make sure you all understand a few basic concepts of electricity. I can’t teach you new material if you don’t know the language, right?
Terminology:
Voltage
The first term is, of course, voltage. Voltage is defined as the difference in electrical potential between two points. What does that mean, I’m sure you wonder? Well, to put it simply, think of a fire hydrant. When the valve is opened to let water into a hose, from the hydrant, it rushes in all at once to the end of the hose. It sits there in the hose until the nozzle is opened to put out the fire. The force that pushes the water forward is called water pressure, and like water pressure, voltage pushes the electrical current along as well. So, we will think of voltage itself as the force or pressure being applied behind an electrical current to keep it moving.
Amperage
Next up is the term, amperes. In short this is the electrical current itself. An ampere, or amp for short, is the actual unit of measurement for the amount of electricity passing a single point in a circuit at one time. This might seem confusing, so let’s just keep it simple and think of an amp as the electrical current itself. In the fire hose example, the amperage would be the water inside the hose.
Wattage
Last up is something called a watt. Now, this one can get tricky, so stick with me. A watt literally measures the rate of energy conversion or the transfer of energy. So, essentially, the watt measures the amount of work done over time. This is where it gets tricky and a little confusing. Wattage, in the fire hose example, would be the amount of water that the fire hose can hold. This is the work, or wattage, generated by the hose while operating under a constant flow of water. Now, that’s the tricky part right there. ‘Work’ in this example isn’t a normal 9-5 job. It is, more simply put, the overall capacity of the hose. A normal household lightbulb is rated around 60 watts. This means that while it’s on, it is producing a constant amount of light. This constant amount is 60 watts, which is its peak brightness under constant current.
So, to sum these three terms up as simply as possible, think of voltage as pressure, amperage as the current, and wattage as the capacity.
Example
One final example should help with this analogy. We’ve all seen those wacky waving inflatable arm flailing tubemen before, right? If not, or if you’ve never seen Family Guy before, it’s basically a long, nylon tube that is open at both ends. One end is attached to a fan at the bottom, while the other end is left open for air to escape. When the fan at the bottom is turned on, it begins to generate wind that inflates the tube and causes it to rise off the ground and flail about in the air. In this example, the voltage is the air pressure keeping the tube floating, the wind flowing through the tube is the amperage, and the amount of wind needed to make the tube rise off the ground is called the wattage.
Undervolting:
Myth or fact?
Let’s go ahead and start off with a bang, shall we? First, let me make it clear to you that no matter what people tell you, undervolting your CPU will not magically make your battery last five days longer than it should. I’m not saying it doesn’t save battery at all, because it does. It just doesn’t save as much as you’ve probably been led to believe. On any average smartphone battery under normal conditions, you should not expect an increase of more than a few percent while undervolting.
Does this mean you should stop undervolting altogether? Not at all! Quite the contrary, actually. Undervolting is actually a very good thing for your smart phone when you do it correctly. Undervolting has one major positive effect on your CPU: it will extend the life of your processor by allowing it to do demanding things with lower heat generation. In the tube example from before, undervolting would be like reducing the fan speed as low as possible while still keeping the tube in the air. The air pressure lowers along with the wind current, or amperage. Due to the now lower amount of pressure, the amount of wind being pushed through the tube (amperage, remember?) is lowered slightly as well. This, in turn, prolongs the life of the nylon tube itself by putting less strain on it while it’s flapping around in the breeze. It’s kind of like how a flag flying in the breeze will last longer than one you fly on the back of your truck while you drive down the highway.
Summary:
Now that we’ve learned all this, what does it all mean? Well, going back to the nylon tube example, the tube itself is the CPU. So, all three properties discussed before come into play here around the nylon tube (CPU). The air pressure forces the wind up through the tube and causes the tube to raise in much the same way as the voltage from your battery causes the electrical current to flow along the circuits through the CPU. Wattage is simply the maximum amount of juice flowing from the battery keeping everything running at the same current.
All this nylon tube talk is only here to show you how the act of undervolting your CPU actually affects the processor itself. Yes, it does reduce stress on your CPU. Yes, it does reduce the drain on the battery. No, it will not likely produce a result that you’ve been hyped up to believe. The effects of undervolting your CPU are minimal at best, and should, in my opinion, only be used if you want your CPU to run a bit cooler under demanding tasks, such as using a heavy GPS app, like CoPilot, for a few hours, or while playing graphics intensive games for a while. Outside of that, you may gain about 30 minutes of extra run time on your battery on average (everyone’s phone is different, this is a rough average), or another couple of months of life on your CPU. Keep in mind that CPUs last many years on average under normal use, notwithstanding defects or abuse.
I’m certainly not telling you to avoid undervolting. I undervolt all my devices, including my personal computers. This post is meant to be informative since most people do this without understanding most of the concepts, while they buy into the hype generated around this. My main point is that the main reason you should undervolt is to keep the heat down on your device while you do demanding things. After all, you have a device in your hands today, most likely, that is more powerful than most desktop PCs just a few short years ago. Why wouldn’t you want to get everything out of it?
Bonus example:
Yet another example of voltage and amperage is your own cell phone charger. Most cell phone chargers now are 5V (volt), 1A (ampere/amp) chargers. This means that there are 5 volts pushing the 1 ampere electrical current to your phone over the USB cable. Wattage comes into play here in the electrical outlet. Most US electrical outlets are rated at 125 watts. Most cell phones are rated at 4-5W (watts) per hour. This means, that the outlet will still have a capacity of 120 or so watts per hour left over while your phone is charging.
How to undervolt:
The procedure for undervolting is different for each device (normally), so I’m not going to show anyone how to do it here. There are a few apps on the market that can help you do it if your kernel supports this feature. If you don’t know if your kernel supports this feature, please ask your ROM chef. Most, if not all, stock ROMs do not support this.
Apps:
The following apps will allow you to tweak your voltage settings if your kernel/ROM allow it. Root is required. There are many more on the market, but these are a few of the most popular ones.
System Tuner Pro
Set CPU
Voltage Control
IncrediControl
Reserved
Thanks for the info CFB
Sent from my GT-I9300 using Tapatalk 2
cajunflavoredbob said:
Introduction:
If you’re reading this, I’m going to assume that you want to learn something new. I love sharing knowledge with others, so I hope you do as well. With that being said, please understand that I’m doing this in my spare time, and have no degree of any kind on this topic. What I’ve compiled here is a pretty good guide to explain and hopefully educate some of you on a highly talked about, but widely misunderstood concept of CPU architecture.
Before we begin, I need to make sure you all understand a few basic concepts of electricity. I can’t teach you new material if you don’t know the language, right?
Terminology:
Voltage
The first term is, of course, voltage. Voltage is defined as the difference in electrical potential between two points. What does that mean, I’m sure you wonder? Well, to put it simply, think of a fire hydrant. When the valve is opened to let water into a hose, from the hydrant, it rushes in all at once to the end of the hose. It sits there in the hose until the nozzle is opened to put out the fire. The force that pushes the water forward is called water pressure, and like water pressure, voltage pushes the electrical current along as well. So, we will think of voltage itself as the force or pressure being applied behind an electrical current to keep it moving.
Amperage
Next up is the term, amperes. In short this is the electrical current itself. An ampere, or amp for short, is the actual unit of measurement for the amount of electricity passing a single point in a circuit at one time. This might seem confusing, so let’s just keep it simple and think of an amp as the electrical current itself. In the fire hose example, the amperage would be the water inside the hose.
Wattage
Last up is something called a watt. Now, this one can get tricky, so stick with me. A watt literally measures the rate of energy conversion or the transfer of energy. So, essentially, the watt measures the amount of work done over time. This is where it gets tricky and a little confusing. Wattage, in the fire hose example, would be the amount of water that the fire hose can hold. This is the work, or wattage, generated by the hose while operating under a constant flow of water. Now, that’s the tricky part right there. ‘Work’ in this example isn’t a normal 9-5 job. It is, more simply put, the overall capacity of the hose. A normal household lightbulb is rated around 60 watts. This means that while it’s on, it is producing a constant amount of light. This constant amount is 60 watts, which is its peak brightness under constant current.
So, to sum these three terms up as simply as possible, think of voltage as pressure, amperage as the current, and wattage as the capacity.
Example
One final example should help with this analogy. We’ve all seen those wacky waving inflatable arm flailing tubemen before, right? If not, or if you’ve never seen Family Guy before, it’s basically a long, nylon tube that is open at both ends. One end is attached to a fan at the bottom, while the other end is left open for air to escape. When the fan at the bottom is turned on, it begins to generate wind that inflates the tube and causes it to rise off the ground and flail about in the air. In this example, the voltage is the air pressure keeping the tube floating, the wind flowing through the tube is the amperage, and the amount of wind needed to make the tube rise off the ground is called the wattage.
Undervolting:
Myth or fact?
Let’s go ahead and start off with a bang, shall we? First, let me make it clear to you that no matter what people tell you, undervolting your CPU will not magically make your battery last five days longer than it should. I’m not saying it doesn’t save battery at all, because it does. It just doesn’t save as much as you’ve probably been led to believe. On any average smartphone battery under normal conditions, you should not expect an increase of more than a few percent while undervolting.
Does this mean you should stop undervolting altogether? Not at all! Quite the contrary, actually. Undervolting is actually a very good thing for your smart phone when you do it correctly. Undervolting has one major positive effect on your CPU: it will extend the life of your processor by allowing it to do demanding things with lower heat generation. In the tube example from before, undervolting would be like reducing the fan speed as low as possible while still keeping the tube in the air. The air pressure lowers along with the wind current, or amperage. Due to the now lower amount of pressure, the amount of wind being pushed through the tube (amperage, remember?) is lowered slightly as well. This, in turn, prolongs the life of the nylon tube itself by putting less strain on it while it’s flapping around in the breeze. It’s kind of like how a flag flying in the breeze will last longer than one you fly on the back of your truck while you drive down the highway.
Summary:
Now that we’ve learned all this, what does it all mean? Well, going back to the nylon tube example, the tube itself is the CPU. So, all three properties discussed before come into play here around the nylon tube (CPU). The air pressure forces the wind up through the tube and causes the tube to raise in much the same way as the voltage from your battery causes the electrical current to flow along the circuits through the CPU. Wattage is simply the maximum amount of juice flowing from the battery keeping everything running at the same current.
All this nylon tube talk is only here to show you how the act of undervolting your CPU actually affects the processor itself. Yes, it does reduce stress on your CPU. Yes, it does reduce the drain on the battery. No, it will not likely produce a result that you’ve been hyped up to believe. The effects of undervolting your CPU are minimal at best, and should, in my opinion, only be used if you want your CPU to run a bit cooler under demanding tasks, such as using a heavy GPS app, like CoPilot, for a few hours, or while playing graphics intensive games for a while. Outside of that, you may gain about 30 minutes of extra run time on your battery on average (everyone’s phone is different, this is a rough average), or another couple of months of life on your CPU. Keep in mind that CPUs last many years on average under normal use, notwithstanding defects or abuse.
I’m certainly not telling you to avoid undervolting. I undervolt all my devices, including my personal computers. This post is meant to be informative since most people do this without understanding most of the concepts, while they buy into the hype generated around this. My main point is that the main reason you should undervolt is to keep the heat down on your device while you do demanding things. After all, you have a device in your hands today, most likely, that is more powerful than most desktop PCs just a few short years ago. Why wouldn’t you want to get everything out of it?
Bonus example:
Yet another example of voltage and amperage is your own cell phone charger. Most cell phone chargers now are 5V (volt), 1A (ampere/amp) chargers. This means that there are 5 volts pushing the 1 ampere electrical current to your phone over the USB cable. Wattage comes into play here in the electrical outlet. Most US electrical outlets are rated at 125 watts. Most cell phones are rated at 4-5W (watts) per hour. This means, that the outlet will still have a capacity of 120 or so watts per hour left over while your phone is charging.
How to undervolt:
The procedure for undervolting is different for each device (normally), so I’m not going to show anyone how to do it here. There are a few apps on the market that can help you do it if your kernel supports this feature. If you don’t know if your kernel supports this feature, please ask your ROM chef. Most, if not all, stock ROMs do not support this.
Apps:
The following apps will allow you to tweak your voltage settings if your kernel/ROM allow it. Root is required. There are many more on the market, but these are a few of the most popular ones.
System Tuner Pro
Set CPU
Voltage Control
IncrediControl
Click to expand...
Click to collapse
Great post but I still have a few questions - How do we know what are safe values to undervolt to and what aren't? I'm on the HTC Mecha so my issue may be slightly different.
Klonopin said:
Great post but I still have a few questions - How do we know what are safe values to undervolt to and what aren't? I'm on the HTC Mecha so my issue may be slightly different.
Click to expand...
Click to collapse
Re-read the heading in the OP that says "How to undervolt."
Great guide for anyone wanting to learn about undervolting and CPU. So simply stated that Even an apple user could understand this. :thumbup:
AT&T SGS3
ParanoidKangDroid 1.1.0
KT747 10/28 OC'ed & UV'ed
Medical MJ Supporter
Dankest said:
Great guide for anyone wanting to learn about undervolting and CPU. So simply stated that Even an apple user could understand this. :thumbup:
AT&T SGS3
ParanoidKangDroid 1.1.0
KT747 10/28 OC'ed & UV'ed
Medical MJ Supporter
Click to expand...
Click to collapse
Aww. That's not nice. Lol
cajunflavoredbob said:
Introduction:
If you’re reading this, I’m going to assume that you want to learn something new. I love sharing knowledge with others, so I hope you do as well. With that being said, please understand that I’m doing this in my spare time, and have no degree of any kind on this topic. What I’ve compiled here is a pretty good guide to explain and hopefully educate some of you on a highly talked about, but widely misunderstood concept of CPU architecture.
Before we begin, I need to make sure you all understand a few basic concepts of electricity. I can’t teach you new material if you don’t know the language, right?
Terminology:
Voltage
The first term is, of course, voltage. Voltage is defined as the difference in electrical potential between two points. What does that mean, I’m sure you wonder? Well, to put it simply, think of a fire hydrant. When the valve is opened to let water into a hose, from the hydrant, it rushes in all at once to the end of the hose. It sits there in the hose until the nozzle is opened to put out the fire. The force that pushes the water forward is called water pressure, and like water pressure, voltage pushes the electrical current along as well. So, we will think of voltage itself as the force or pressure being applied behind an electrical current to keep it moving.
Amperage
Next up is the term, amperes. In short this is the electrical current itself. An ampere, or amp for short, is the actual unit of measurement for the amount of electricity passing a single point in a circuit at one time. This might seem confusing, so let’s just keep it simple and think of an amp as the electrical current itself. In the fire hose example, the amperage would be the water inside the hose.
Wattage
Last up is something called a watt. Now, this one can get tricky, so stick with me. A watt literally measures the rate of energy conversion or the transfer of energy. So, essentially, the watt measures the amount of work done over time. This is where it gets tricky and a little confusing. Wattage, in the fire hose example, would be the amount of water that the fire hose can hold. This is the work, or wattage, generated by the hose while operating under a constant flow of water. Now, that’s the tricky part right there. ‘Work’ in this example isn’t a normal 9-5 job. It is, more simply put, the overall capacity of the hose. A normal household lightbulb is rated around 60 watts. This means that while it’s on, it is producing a constant amount of light. This constant amount is 60 watts, which is its peak brightness under constant current.
So, to sum these three terms up as simply as possible, think of voltage as pressure, amperage as the current, and wattage as the capacity.
Example
One final example should help with this analogy. We’ve all seen those wacky waving inflatable arm flailing tubemen before, right? If not, or if you’ve never seen Family Guy before, it’s basically a long, nylon tube that is open at both ends. One end is attached to a fan at the bottom, while the other end is left open for air to escape. When the fan at the bottom is turned on, it begins to generate wind that inflates the tube and causes it to rise off the ground and flail about in the air. In this example, the voltage is the air pressure keeping the tube floating, the wind flowing through the tube is the amperage, and the amount of wind needed to make the tube rise off the ground is called the wattage.
Undervolting:
Myth or fact?
Let’s go ahead and start off with a bang, shall we? First, let me make it clear to you that no matter what people tell you, undervolting your CPU will not magically make your battery last five days longer than it should. I’m not saying it doesn’t save battery at all, because it does. It just doesn’t save as much as you’ve probably been led to believe. On any average smartphone battery under normal conditions, you should not expect an increase of more than a few percent while undervolting.
Does this mean you should stop undervolting altogether? Not at all! Quite the contrary, actually. Undervolting is actually a very good thing for your smart phone when you do it correctly. Undervolting has one major positive effect on your CPU: it will extend the life of your processor by allowing it to do demanding things with lower heat generation. In the tube example from before, undervolting would be like reducing the fan speed as low as possible while still keeping the tube in the air. The air pressure lowers along with the wind current, or amperage. Due to the now lower amount of pressure, the amount of wind being pushed through the tube (amperage, remember?) is lowered slightly as well. This, in turn, prolongs the life of the nylon tube itself by putting less strain on it while it’s flapping around in the breeze. It’s kind of like how a flag flying in the breeze will last longer than one you fly on the back of your truck while you drive down the highway.
Summary:
Now that we’ve learned all this, what does it all mean? Well, going back to the nylon tube example, the tube itself is the CPU. So, all three properties discussed before come into play here around the nylon tube (CPU). The air pressure forces the wind up through the tube and causes the tube to raise in much the same way as the voltage from your battery causes the electrical current to flow along the circuits through the CPU. Wattage is simply the maximum amount of juice flowing from the battery keeping everything running at the same current.
All this nylon tube talk is only here to show you how the act of undervolting your CPU actually affects the processor itself. Yes, it does reduce stress on your CPU. Yes, it does reduce the drain on the battery. No, it will not likely produce a result that you’ve been hyped up to believe. The effects of undervolting your CPU are minimal at best, and should, in my opinion, only be used if you want your CPU to run a bit cooler under demanding tasks, such as using a heavy GPS app, like CoPilot, for a few hours, or while playing graphics intensive games for a while. Outside of that, you may gain about 30 minutes of extra run time on your battery on average (everyone’s phone is different, this is a rough average), or another couple of months of life on your CPU. Keep in mind that CPUs last many years on average under normal use, notwithstanding defects or abuse.
I’m certainly not telling you to avoid undervolting. I undervolt all my devices, including my personal computers. This post is meant to be informative since most people do this without understanding most of the concepts, while they buy into the hype generated around this. My main point is that the main reason you should undervolt is to keep the heat down on your device while you do demanding things. After all, you have a device in your hands today, most likely, that is more powerful than most desktop PCs just a few short years ago. Why wouldn’t you want to get everything out of it?
Bonus example:
Yet another example of voltage and amperage is your own cell phone charger. Most cell phone chargers now are 5V (volt), 1A (ampere/amp) chargers. This means that there are 5 volts pushing the 1 ampere electrical current to your phone over the USB cable. Wattage comes into play here in the electrical outlet. Most US electrical outlets are rated at 125 watts. Most cell phones are rated at 4-5W (watts) per hour. This means, that the outlet will still have a capacity of 120 or so watts per hour left over while your phone is charging.
How to undervolt:
The procedure for undervolting is different for each device (normally), so I’m not going to show anyone how to do it here. There are a few apps on the market that can help you do it if your kernel supports this feature. If you don’t know if your kernel supports this feature, please ask your ROM chef. Most, if not all, stock ROMs do not support this.
Apps:
The following apps will allow you to tweak your voltage settings if your kernel/ROM allow it. Root is required. There are many more on the market, but these are a few of the most popular ones.
System Tuner Pro
Set CPU
Voltage Control
IncrediControl
Click to expand...
Click to collapse
thanks for the information!!!
Good job guys. Why don't I requote the entire passage to thank the op instead of hitting the thanks button.
Sent from my GT-N7000 using Xparent ICS Tapatalk 2
hariskoirala said:
thanks for the information!!!
Click to expand...
Click to collapse
Thanks for quoting a long post like a douchebag.
Markuzy said:
Good job guys. Why don't I requote the entire passage to thank the op instead of hitting the thanks button.
Sent from my GT-N7000 using Xparent ICS Tapatalk 2
Click to expand...
Click to collapse
Oh, please do. You're not cool unless you do it. /sarcasm
I don't understand those guys...
cajunflavoredbob said:
Thanks for quoting a long post like a douchebag.
Click to expand...
Click to collapse
He's probably post farming with useless "Thanks/me too/excellent/this is useful" posts to get the min 10 posts...
All such people should be reported.
Markuzy said:
He's probably post farming with useless "Thanks/me too/excellent/this is useful" posts to get the min 10 posts...
All such people should be reported.
Click to expand...
Click to collapse
Probably so. Those guys don't understand how easy it is to make ten useful posts.
Epic thanks for the guide its pretty easy for dummies like me to follow
nikufellow said:
Epic thanks for the guide its pretty easy for dummies like me to follow
Click to expand...
Click to collapse
I'm glad you enjoyed it. I was hoping to make it as simple as possible. I'm glad it worked.
Very useful info
Thanks
Sent from my ST25i using Tapatalk 2
Really informative thread. Helped clear a lot of confusions. Wish everyone explained things this nicely.
Very nice. Thanks be clicked.
WHO DAT!!
Can you please tell a rough estimate of safe range. Or is there no danger in undervolting?
Sent from my IM-A770K using xda app-developers app
When I undervolt, I do a little at a time and make sure things are stable before trying again.. Make sure u do a nandroid and if u have any trouble, you can always boot into recovery and restore if u can't change ur voltages back to where they were stable.. Just my 2¢
From my rat infested note ii
Hello guys
I'm not a new user in kernels or ROMs .
I have a low-decent battery life ,and I'm sure there's a way to get a better battery life with undervolting .
I want to know
what is "undervolting" ?
What is the biggest damage it can cause?
What is PVS?
How do I know ,how much I can UV?
What are the steps to undervolt?
What I gain from UV (despite battery life)?
For your info ,I'm using AOSPAL ROM +FAUX's latest 16u kernel .
Thanks
Sent from my Nexus 5 using XDA Premium 4 mobile app
http://forum.xda-developers.com/showthread.php?t=2537000
Sent from my Nexus 5 using Tapatalk
Hi,
Most of your questions have a reply:
About undervolting: http://forum.xda-developers.com/google-nexus-5/general/nexus-5-undervolting-thread-t2537000.
CPU binning: http://forum.xda-developers.com/google-nexus-5/general/cpu-binning-nexus-5-t2515593.
The "risks" are instability like hard reboot, SOD, etc.... To find a "safe" value you will need to test by yourself to find what undervolting your CPU can handle, not all CPU's are equals.
Undervolt by steps like - 25mV, don't set your new values at boot unless your are sure it's stable (or you could encounter bootloop), test for a few days under different conditions (as your use).
The gain apart battery life (but you will not gain that much as people tend to think) is a little less heat, but again nothing huge..., better is to test by yourself and see what you will gain... or not.
Battery life depends mainly of your use, apps, signal quality and settings like, screen brightness, synchro, CPU governor, etc... In my opinion check first what could be the cause of your low battery life (and what is low battery life for you???) before play with undervolting.
As said above, undervolting will get you very minor battery life increases.
More than likely you have an issue, or its just your setup and usage giving you the battery life you are seeing.
Undervolting will not change any of this.... You'll gain only minutes of battery time.
Try some troubleshooting in the below thread to see if you have an issue, or how to setup for better battery life. Read through it a bit, from the last page and work back a bit. You can post meaningful screenshots there too. From gsam or BBS.... not the stock battery screen, it has no real useful info for finding issues. Good luck!!
http://forum.xda-developers.com/showthread.php?t=2509132
Nexus 5 Battery Results
I've been undervolting many systems for many years, primarily Linux desktops and some servers, and the primary benefit is that you get less heat output which means when running cpu-intensive tasks the temperature climbs slower so the throttling of the clockspeed kicks in later, so your phone will be faster in certain situations. If you take a phone which has been idle for a while and run a benchmark, and then immediately run that benchmark again, the 2nd time gets a lower result as the phone is still hot from the 1st. This makes drawing conclusions about settings really dificult but it illustrate that throttling from heat is affecting speed.
For most users their perception will be the phone runs cooler.
You do undervolt at each step in the processor's frequency, and each step is a trial+error activity, the throttling I mention means finding a stable under-volt at the higher frequency which is labour-intensive,i.e take the max clock, and undervolt it a little, run a benchmark which forces it to run at high clockspeed, and if it passes that test then run it again at the next step down in frequency. Once you've got the most stable top clockspeed, then do it progressively for all the other voltages on the way down.
In some platforms in Linux and Windoze, we wrote scripts which save the stable voltages and then undervolts a little and runs a stress-testing benchmark and if the system hung it wouldn't save the current voltages so the previous higher voltages were safer, stick that script in a startup script area and leave the compute to do many self resets, and you've calculated your device's voltage range. I wonder if someone has that done for Android??? For a laptop the FAN would run slower saving battery time and for laptops that would lead to say 20% better battery life but on a phone it won't make much saving as no fan.
Your phone will run most of its time (like 95%) at its lowest frequency, so for effort/benefit just focusing on dropping its voltage will gain the most in the phone running cooler.
Battery life improvement is marginal, if you look at your battery stats its down to your application settings and screen brightness, i.e. how you use and what you do with your phone. So if your battery life is bad, use your phone less!
I carry a slim USB battery, it is the $/effort/benefit the best thing you can do, $20 doubles your battery life, if you get one with a 1.5A-2A output in just a few minutes when the phone doesn't mind a battery attached, will dwarth every possible tweak and hack anyone can form in benefit.