Suspend vs. Lock vs. Screen Off

David Pottage david at
Thu Oct 2 21:32:35 CEST 2008

Jason Cawood wrote:
> I'm using the latest FDOM, I believe it's based on 2008.09.  My question is
> what is the fundamental difference between pressing the power button to
> cause the phone to suspend, pressing the aux button to make the phone lock
> the screen and not pressing any buttons and letting the software timeout. 
> Mainly, I'm interested in battery life and how each action reduces power
> consumption. 
When the device suspends Linux gets suspended to RAM in the same way as 
you can suspend most laptops. In this state the CPU and memory use very 
little power. The GSM module and parts of the chipset remain powered, so 
you should will still receive incoming calls and SMS messages. The idea 
is that the Main CPU will wake up if it receves and interupt from the 
GSM module, the power key or from varous other sources, but the rest of 
the time it will be suspended and use little power. This creates the 
illusion of being always on, but in fact only being on when the user is 
trying to use the device. Most modern GSM handsets work in the same way.

If you leave the device without pressing any buttons the screen 
backlight will go out. This saves a substantial amount of power but not 
as much as suspending. Depending on your settings, your freerunner may 
suspend after a time with the backlight out.

Pressing the Aux key to lock the screen does just that. The phone will 
turn out the back light or suspend according to it's settings.

David Pottage

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