On Tuesday, April 3, 2012 12:03:02 AM UTC-4, Put_tiMe wrote: > > So according to Dianne's post, CPU is indeed completely switched off. > And in Android, there is no CPU under clock mode. > And it can be woken up only by external interrupts. Got that. > > But then how does Alarm-manager timers work? > Is it some kind of delayed interrupt or something like that? i.e an > interrupt that will be raised after some time??? > I thought at least the alarm-manager will need the CPU running. >
Most embedded chips, especially those intended for battery powered systems, have various peripherals such as timers external to the cpu core which can continue to operate even when the cpu core is powered down. In the chips used in most contemporary smartphones, one of those "peripherals" is actually an entire additional arm processor core, charged with running the radio and other things such as low level audio and button I/O. The power state of that processor is quite independent of the power state of the application arm processor which runs the Linux kernal, android stack, and SDK apps, so checking in with the mobile network infrastructure does not involve waking up the application processor. (Depending on your perspective, the argument could be made that the radio processor is actually the heart of the system, with the application processor just being a fancy peripheral charged with entertaining the user...) -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
