[Nexus 5 Original Android Development] big_adventure:
I am guilty of simplifying to express the point, it's true, but...

Unfortunately, that isn't really how it works in practice. Chips made on the same fab leak differently. This is why there are different bins of Snapdragon 800's - some at 2.26, some at 2.1, some at 2.0. The next rev is supposed to be 2.4. And even than, inside the "2.26" chips, there are what, 5 different bins supported by Qualcomm as "OK" at that speed? Basically, leakage is NOT providing quadratic power consumption at that conservative, totally-supported clocking, since the chip is optimized to run at that speed.

The chips in our phones will run cleanly and hapilly, at any "supported" bin (1-5), at 1v @ 2.26Ghz. This is the "conservative" UV that most people seem to run. They also run 1.57Ghz at 875mv - again, the conservative, -50UV. And yes, that isn't exactly linear - actual consumption is going to be more than just the 12% difference in voltage.

There is no doubt that the phone consumes more energy at 2.26ghz than at 1.56Ghz. It's stupid to say otherwise. But that's not the question here - if you are reading a webpage, or reading a book, or reading a facebook post, the phone should be at 300Mhz while inactive but in use. No, it's not sleeping, but it doesn't matter - that idle is going to use the same energy on a phone set to max out at 2.26 or a phone set to max out at 1.5.

...and this is the most important part...

It's just that, turning pages, rendering images, loading assets, etc., all require the phone to clock up. And, this is critical, the phone isn't just clocking up the CPU - it's also going to run the GPU for longer (since the GPU is going to be stuck waiting around for the CPU more), it's going to run the memory at higher speed for longer, it's probably going to need to run the radio longer in the case of browsing the web or facebook - it's going to spend more time powering basically everything that can normally be power-gated. And the phone is going to spend about a third or more less time clocked up from 300 if it can max out to 2.26 than if it's stuck at 1.5. So it's still a race-to-idle situation, even if idle here isn't sleep.

Now, if you OC'd the chip well out of it's efficient range, you'd get vastly different results.

But you don't have to take my word for it. Try it yourself. It isn't hard - just waste two days of your life sitting in front of your phone. Spend day one reading a book or browsing the web with max at 2.26, and spend day 2 with a max of 1.5. This test is obviously totally invalid for gaming - it only applies to situations where the phone's got the chance to drop voltages to idle levels and, equally importantly, power-gate thirsty components faster. I ran a light version of the test this morning, reading a book in Kindle and listening to music in the background, and ignoring notifications, just an hour at each setting, to verify. I used 17 fewer MV according to the battery settings page under *#*#4636#*#* with the full clock. Now, this is not a perfect test - I can't assure that I had the same number of notifications both ways, can't assure that everything was perfectly equal, can't even assure the same number of page-turns, and the difference was slight. If I get the chance, I'll repeat testing for longer periods and repost the information.