Rockbox Technical Forums

Rockbox Development => Feature Ideas => Topic started by: delt on August 10, 2008, 04:50:14 PM

Title: CPU speed user-configurable
Post by: delt on August 10, 2008, 04:50:14 PM
Hello,

Currently we have to change the speed in the source code (at least on the ipod nano port) ... i was wondering if it was possible to make this a runtime-configurable parameter instead of hard-coded (might need to reboot the player to run at the new speed)

It would be quite useful i think, for tweaking battery usage.
Title: Re: CPU speed user-configurable
Post by: bluebrother on August 10, 2008, 05:02:02 PM
Why would it be useful and why do you have to adjust the cpu speed anyway? During normal operation Rockbox switches between two cpu frequencies for exact the same reason: saving power. This is working pretty well.

Allowing users to manually adjust the used frequencies is doomed to make it work worse ...
Title: Re: CPU speed user-configurable
Post by: saratoga on August 10, 2008, 05:44:50 PM
This would only be misused.  People with an actual use for it can just change the source code.
Title: Re: CPU speed user-configurable
Post by: delt on August 10, 2008, 11:29:59 PM
So as i understand it, downclocking the CPU won't save much battery power, right? If rockbox uses idle calls, that's fairly logical, since any operation will require the same number of cycles, just slower.
Title: Re: CPU speed user-configurable
Post by: saratoga on August 10, 2008, 11:41:25 PM
So as i understand it, downclocking the CPU won't save much battery power, right? If rockbox uses idle calls, that's fairly logical, since any operation will require the same number of cycles, just slower.


Rockbox doesn't idle typically, it just lowers the CPU clock.  The whole idea of lowering the limit on how far down the average clock can go is to save power in codecs that are already running real time at the lowest allowed clock speed (current 30MHz on PP targets).

Did you look at the tracker?  There should be plenty of info there.