NexusHD2 Android Forum

How often have you heard someone say that you can save a bit of battery life if you lower your minimum CPU frequency from 384 to 245 or to 128MHz, etc.? The lower you go, the greater the chance is that you will see follow-up posts complaining that the device will not boot, it freezes, whatever.

Note that there is no difference in voltage used when looking at the CPU frequency range between 96MHz-460MHz.

I really do not know where this all started, but experiment for yourself. Look at the chart I put together, by looking at HD2 default settings and comparing them to those provided by Tyween many moons ago, for a different HD2 ROM (offered as an example only – it did work for me then, but I have not embarked down that path recently). I offer no opinion on which works best for the HD2. See what works best for yours.



Do not limit yourself to Tyween's suggestions... Have fun, and remember that after all, they are only suggestions.

MarkAtHome wrote:How often have you heard someone say that you can save a bit of battery life if you lower your minimum CPU frequency from 384 to 245 or to 128MHz, etc.? The lower you go, the greater the chance is that you will see follow-up posts complaining that the device will not boot, it freezes, whatever.

Note that there is no difference in voltage used when looking at the CPU frequency range between 96MHz-460MHz.

You are right - this is an age old topic, not unlike Task29, format and a host of others.

Too many have used SetCPU to lower the frequency too much and not have the device wake from sleep. This used to be a recurring topic, of course (it likely still is).

The one thing that comes to mind is that while your suggestion of experimenting is fine I am convinced some people whoelect to experiment and, as a result, experience problems, may not know how to rectify the situation later. Just a warning to the wise..

NYLimited wrote:
You are right - this is an age old topic, not unlike Task29, format and a host of others.

Too many have used SetCPU to lower the frequency too much and not have the device wake from sleep. This used to be a recurring topic, of course (it likely still is).

The one thing that comes to mind is that while your suggestion of experimenting is fine I am convinced some people whoelect to experiment and, as a result, experience problems, may not know how to rectify the situation later. Just a warning to the wise..

Ok, than add "Grasshoppers need not apply. Must have, at least, a decade or two of experience or masters degree in computer science or brain surgery, to try this." Better?

MarkAtHome wrote:Ok, than add "Grasshoppers need not apply. Must have, at least, a decade or two of experience or masters degree in computer science or brain surgery, to try this." Better?

I would settle for common sense but as I always said common sense is not so common.




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You can chose to ignore reality, but you cannot ignore the consequences of ignoring reality.

MarkAtHome wrote:How often have you heard someone say that you can save a bit of battery life if you lower your minimum CPU frequency from 384 to 245 or to 128MHz, etc.? The lower you go, the greater the chance is that you will see follow-up posts complaining that the device will not boot, it freezes, whatever.

Note that there is no difference in voltage used when looking at the CPU frequency range between 96MHz-460MHz.

I really do not know where this all started, but experiment for yourself. Look at the chart I put together, by looking at HD2 default settings and comparing them to those provided by Tyween many moons ago, for a different HD2 ROM (offered as an example only – it did work for me then, but I have not embarked down that path recently). I offer no opinion on which works best for the HD2. See what works best for yours.



Do not limit yourself to Tyween's suggestions... Have fun, and remember that after all, they are only suggestions.

Are there any numbers or findings on how much lowering the voltages affect battery life? I will play with voltages soon but any preinformation is highly appreciated

It depends of your usage pattern. There is no straight answer. You have to try yourself. Some time ago I had my HD2 strongly underclocked (96mhz@800mA when screen off). Later I changed minimal freq to 460mhz@1000mA. CurrentWidget reported, that my HD2 had 3mA battery drain while undercloked and 4mA while using 460mhz as min value.
So there was some difference.

However both ways I had to charge phone overnight, so for me the difference was not significant

I thought that setting min cpu below 245 was a waste of time, see http://forum.xda-developers.com/showpos ... tcount=935

Robbie P wrote:I thought that setting min cpu below 245 was a waste of time, see http://forum.xda-developers.com/showpos ... tcount=935

Well, unless you change the default voltages, setting the min CPU to anything lower than 460MHz would be a waste of time, since all voltages up to and including 460MHz defaults to 1000mv -- you are using the same amount of power, so why cap the CPU speed to anything below 460MHz?

It might be better to ask at what voltage that 245MHz was associated with. Setting min cpu below 245 being a waste of time might very well be true if voltages were set to something other than the default.

Code: Select all

echo "96000 800" > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '128000 825' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '245000 825' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '384000 875' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '422400 900' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '460800 925' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '499200 950' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '537600 975' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '576000 1000' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '614400 1025' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '652800 1050' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '691200 1075' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '729600 1100' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '768000 1100' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '806400 1125' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '844800 1150' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '883200 1150' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '921600 1175' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '960000 1175' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '998400 1200' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '1036800 1200' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '1075200 1225' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '1113600 1225' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '1152000 1250' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '1190400 1275' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels

Voltage table, that I used some time ago. However I was using it with some (complicated) profile schema created in setcpu. Just setting this table and min freq in preferences probably will hang your HD2 pretty fast

The 96mhz speed was used only with screen off (last step before cpu going to sleep). Any action should force profile with min freq 245mhz to avoid black screen bug (or even more, depending on your own HD2 - underclocking is similar to overclocking, what one cpu can do maybe completely bed for other one).

MarkAtHome wrote:Well, unless you change the default voltages, setting the min CPU to anything lower than 460MHz would be a waste of time, since all voltages up to and including 460MHz defaults to 1000mv -- you are using the same amount of power, so why cap the CPU speed to anything below 460MHz?

It might be better to ask at what voltage that 245MHz was associated with. Setting min cpu below 245 being a waste of time might very well be true if voltages were set to something other than the default.

Power consumption in a CMOS device is proportional to the frequency at wich it operates.
power consumption also goes with the sqare of voltage.
so reducing the voltage is more effective than reducing the clock speed, nevertheless reducing the clock speed reduces the power consumption.