[Sprint Samsung Galaxy S III] mw86:
Well said Jim thank you for your contribution :) glad to see you continue to be one of those who participate i discussion. Im on gs4 exynos and its almost same observation. Some ways undervolt has caused me nothing but issues even if ever so hard to notice. Seems like the best idea of undervolt is just to cool down some high mhz if stock mv keeps that frequency to hot, the limit being when it starts to destabilize.

Cpus have worked same forever. I take a quote from my stweaks app with a voltage note. Personally statement holds true for all hardware.

"Decreasing voltage will lower the power consumption of the cpu. Increasing it on overclocked frequencies improves stability. Too low voltages may cause instabilities and freezes."

-When undervolting you are deviating from what has already been proven to be free of instabilities and freezes. If you push too far there is no other result than those issues. Some instabilities really effect data rates as a mobile data radio can push a cpu harder in a download in a split millisecond vs even some benches. Sometimes you'd not know and just see data signal loss or download should be working and just keeps getting 0kbs...

-When overclocking or undervolting there is usually two types of typical instabilities. One way the device freezes (screen displays last activity) (*holding power button for 4 seconds forces power off or battery removal) , screen goes black not from user inactivity, stays this way when should be on and toggling screen on fails) (*holding power button for 4 seconds forces power off or battery removal) and the luckier crash and reboot as atleast phone is returned to running state immediately.

The less typical type of instability is sometimes experienced before the point one find true stability in everything. Apps could crash to home screen or glitch in user interface functions, messages or data sent through radios may fail since cpu is sending erroneous data either read or written where accuracy is key which is in almost all cases. These cpus and hardware luckily has error correction so the occasional data that is nit accurate is fixed while calculations continue. If you push below stable thresholds this will start being used and may feel stable but in all cases when it really is happening regularly will slow down cpu far more than in some cases cutting mhz in HALF. The idea is never have need of error correction and have it to protect you not hold you from falling because you happen to be right at the cliffs edge. If you want cpu to run optimally its like a race car and straight lines. Holes in the road are errors and error correction is the work crew ahead of you fixing those things ahead of you to continue on. You must wait for them while they fix, slowing you from where you'd be without these holes in th road. So for a faster trip for the cpu keep stability the first and foremost concern even over battery life, because STABILTY effects BATTERY LIFE just as much or more than a governor being more or less efficient at controlling mhz.

Btw guys its been tested from what ive seen that on a workload matched to the capabilities of say 378mhz set to 1200mv and same one on 1512mhz set to 1200mv and the workload is on going the later takes much more power than the 378mhz at 1200mv and shockingly very close to the same power taken on 378mhz [MENTION=1348102]1200[/MENTION]mv vs 378mhz @ 900mv on the Arm chips.

*as a rule of thumb higher mhz regardless of voltage set will take more power than a lower mhz on same workload.

The only way that doesn't hold true is more related to a workload itself, being if a low mhz takes so much time to complete a big workload vs a high mhz it can eventually take more power at the lower mhz just because that mhz is just inefficient for high workloads hence why we raise and lower mhz based on percent cpu load otherwise inefficiency would be met immediately when a given mhz is overloaded. This is why a governor thats smart is key. You want to linger on low mhz if you can anytime ypu can it will always save you the most power and when things get too much you definitely want more speed to get the job done even if the mhz is going to start to take more power.

-a cpu core will always take more power when it nears 80-100% load then if it just was dealing with a 20-50% load regardless of mhz pertaining to this aspect. Again a good reason a smart governor is important to match mhz to workloads.

Inherently from the above statements you can combine the infos. A cpu at high 100% load will take more power but if that mhz is getting the job done fast enough it would save more power than raising mhz since that would always require more power, but if its too slow at such a load an increase of mhz would be warranted and best only as little increase as possible to be mindful of power. That governor holding you at low mhz under a heavier load playing music as example will save most as long as it dont stress the cores too much vs a governor playing music jumping often to peaks in high mhz. Time is also key, better jump up to target mhz get job done and return as fast as possible to the target cpu load at low mid mhz. As long as sample rate allows cpu load to see a change from the changed mhz which governor chose than as fast a sample rate as possible is welcomed. Once it starts to jump up from just small jumps in load it has already been set too low to be accurate to workloads anymore.

I jumped all around on subject and info and the following was just experience and observation with no concrete data to base it on other than the few facts such as Arm chips at varied mv on the same mhz will draw close to the same power vs same mhz voltage differed. This only holds true to a certain point as to some extent a voltage far too high will increase uneeded energy and inherently increases heat produced. Ironically increases in heat raise voltage requirements for a given mhz :) as well as increases in battery temperature yield lower battery life. Those not using a throttle control setup in kernel may want to consider to start using such controls to keep temperatures down.