[AT&T Samsung Galaxy Note I717] Jamesyboy:
There's no reason not to under volt.

UC=Under clock

UV=Under volt

OC=Over clock

OV=Over volt.

Newer generations of chips have tremendous tolerances. If you were to look at the S3, a Qualcomm built SoC that was a bit long-in-the-tooth by the time the Note was released, you'd see that in many cases, there were phones that featured the chip, but were clocked lower... I.E at 1,000 MHz.

Most chips are designed to run faster than they do, at least for short periods of time. Modern chips use temperature and load to designate the running frequency.

When Qualcomm releases a chip, they need to be sure that 99% of the units they produce, can run with a near-flawless level of stability. Because of this, they often run chips slower, and at a higher voltage than is actually needed. The result is, that Qualcomm or Samsung might design a chip rated for 2ghz, and release their first device with the chip running at 1.5ghz. This is common. Each piece of silicon is slightly different due to manufacturing differences. Chips are made on giant discs, with hundreds of chips on a single disc. The chips in the center are generally considered to be of a slightly higher quality, requiring less voltage, or capable of running at a higher frequency, sometimes both. Because of this, each device is capable of slightly more, or slightly less. The challenge is for Qualcomm to set the speed and power usage for every chip-- the challenge for us, is to see if we can run the chip at a higher frequency, while drawing less power....because power =heat, and power= battery life.

There are two different ways to approach customizing frequency and voltage to your needs.

One: If you could run your Note at 1,900mhz, instead of 1500mhz, and draw the same amount of power, that'd be considered a success case. Your device would be faster, without a hit in battery life.

Two: Or, if you could run the device at the same speed, and lower the voltage (saving battery life), this would also be considered a success.

Sometimes, but rarely in the mobile space, you'll get lucky and receive a prime piece of silicon, and you'll be able to over clock, WHILE undervolting...resulting in a faster phone that uses battery life.

Ranger was correct...clock speed changes on the order of +/-20 percent are hardly noticeable. However, power requirements grow exponentially at higher frequencies, and on a mobile device, they're noticeable. While a device might require 1.2 volts at 1.5 GHz, and 1.3 at 1.6ghz, it might also only require 1.05, or 1.0 volts at 1.4ghz. These numbers are theoretical, and shouldn't be used-they arent even close to correct. They're used merely to illustrate that to over clock, chips often require more power than over clocking is worth, in heat (and heat past a certain point will instantly fry your device, or will reduce the lifespan of the chip).

These are general ideas on over clocking. If you want to know something specific, ask away. When over clocking/underclocking, the governor used (a set of conditions that tells the CPU when to change from, say 300mhz (when the screen is off, and the device isn't being used), to 1.5ghz, when both cores are being used, and fully loaded.

If you want to save battery life, a combination of build.prop radio tweaks, modem tweaks, under clocking profiles, and using a custom governor can significantly increase standby time, and noticeably, but not too significantly increase usage time. Its important to know though, that the screen is the hungriest part of our device, and brightness is the the quickest setting to adjust to gain battery life.

The same is true for performance. Kernel, OC profiles, build.prop and launcher tweaks, GOU over clocking, etc. All in combination can have a noticeable effect, because performance is the net sum of dozens of moving parts.