Power Consumption

[LeChuck87]

Have a look:

Youtube-Link

..nice to see 15 hours possible!

EDIT: video description added:

MWeston2 — May 05, 2010 — Here's a video showing my ammeter in series with the Pandora battery. I wanted to double check the fuel gauge calibration because with lite settings, 15 hours is being presented. I thought that was crazy, but it's true. With an average current of 278mA and a battery testing at 4200mAh, that really is 15 hours (under specific settings talked about below of course).

Testing was done at 500MHz and the screen brightness set just about as low as it will go before shutting off. Increasing the screen brightness to 100% upped the average current to 398mA which is only 10.5 hours of continuous use.

In the second half, I upped the clock to 750MHz using the little menu option but I'm not certain if it actually did anything. Some stuff seems to work better for other people than me but this little program is one that seems to bug out on me.

This video also shows the power consumption with wifi running. You can see the power go way up when web pages are loaded or when new cover art is loaded in Mplayer. If you load pages and then spend a long time reading them before loading the next one, perhaps 10 hours is still possible. At the max I saw of approx. 600mA, that would be 7 hours and you'd have to be hammering wireless hard to maintain that as you can see. Notaz did a fantastic job of getting the power management for wifi working and it will really help battery life for normal use. I guess it's like any other device you would buy now, but for the developers it's such a thrill to see it working.

 

[Dead1nside]

Very happy. I was getting worried that battery life was going to be under my expectations, it doesn't appear to be. That battery is one of the major reasons I preordered. Unlike Nokia who of late prefer to underpower, under provide. Great work to all involved, notaz, you've done some great power management there in the driver.

 

[r00tw00t]

Wow! Even though we been told amazing battery time, I never thought it would be that good!

edit: Now where is my Pandora?

 

[elwing]

hum, could someone describ the video content? sometimes proxies sucks...


edit: many thanks

 

[WhiteBat]

oops, nevermind

 

[JayFoxRox]

Unless I see the tests I asked for on youtube I'd just label this as "marketing speech" as it's an unrealistic case.
//Edit: Not to mention that the CPU "usage" (there is no such thing - I hate this term..) is very different when emulating something.
The presented test case might be realistic for games with a software renderer which don't do any complex physics etc.
However, nearly anything will either stress the CPU (emulation) and / or use the SGX to draw things.
If you are on the go and you don't have the ability to recharge you won't browse the internet unless you use an USB dongle - that would most likely draw more power than the internal chip.

 

[r00tw00t]

Unless I see the tests I asked for on youtube I'd just label this as "marketing speech" as it's an unrealistic case.
//Edit: Not to mention that the CPU "usage" (there is no such thing - I hate this term..) is very different when emulating something.
The presented test case might be realistic for games with a software renderer which don't do any complex physics etc.
However, nearly anything will either stress the CPU (emulation) and / or use the SGX to draw things.
If you are on the go and you don't have the ability to recharge you won't browse the internet unless you use an USB dongle - that would most likely draw more power than the internal chip.

Yeah, I understand this. Quake3 or similar will draw more power but it's still very impressive in my world

 

[Caine]

Can we crank up battery life by any significant amount by underclocking the CPU (e.g. when emulating old systems like e.g. atari) or is the power draw mainly dominated by the screen?

 

[craigix]

Can we crank up battery life by any significant amount by underclocking the CPU (e.g. when emulating old systems like e.g. atari) or is the power draw mainly dominated by the screen?

The screen does take a big chunk.

However we still have much to do to make the battery life even longer.

Optimisation shall continue in an emulator like way until it's as good as it can possibly be.

 

[Asiyura]

If we can have 10.5 hours of battery at the moment, imagine when the devs will get their pandora.

If battery can provide 2-4 hours of amiga emulator, I would be more than happy
And since this emulator is still not optimized ....

 

[craigix]

If we can have 10.5 hours of battery at the moment, imagine when the devs will get their pandora.

If battery can provide 2-4 hours of amiga emulator, I would be more than happy
And since this emulator is still not optimized ....

You will get over 10 on the Amiga emu.

 

[Grench]

Since you have the ammeter in serial on that rig - can you give us some idea of what it pulls just using mplayer for an MP3 playback and the screen off - i.e. minimum power usage & max hours as an in-flight MP3 player. I know it will be better once the DSP specific mode is figured out, but I'm guessing it's already going to be in the 10s of hours.

Thanks!

 

[EvilDragon]

Well, not tried it, but I know 500 MHz with WiFi and screen off is about 18 - 19 hours.
Playing MP3 with MPlayer does need about 9 - 10% CPU usage (can most probably be made way better, I think it does software decoding currently), so you should be able to go down to 100 - 200 MHz for music playing.

@MWeston:
If you switch to 700MHz, nothing will immediately happen.
AFAIK, Linux and the OMAP scales. You set the MAX speed, but as long as the CPU usage isn't too high, the CPU won't clock to 700MHz. At least that's what I think - but I might be in error there .)

 

[paddy]

@ Ed's post

If you switch to 700MHz, nothing will immediately happen.
AFAIK, Linux and the OMAP scales. You set the MAX speed, but as long as the CPU usage isn't too high, the CPU won't clock to 700MHz. At least that's what I think - but I might be in error there .)


What does that mean Ed ? can i have the system boot up at the highest possible clock speed as default or does it ramp the speed when needed ,i don't really like the sound of the ramp speed clock setting ,is this normal for ARM cpu's.

What i mean is ,i would like to have a full always say 750mhz ,is this possible at bootup and throughout use ?

 

[EvilDragon]

@ Ed's post

If you switch to 700MHz, nothing will immediately happen.
AFAIK, Linux and the OMAP scales. You set the MAX speed, but as long as the CPU usage isn't too high, the CPU won't clock to 700MHz. At least that's what I think - but I might be in error there .)


What does that mean Ed ? can i have the system boot up at the highest possible clock speed as default or does it ramp the speed when needed ,i don't really like the sound of the ramp speed clock setting ,is this normal for ARM cpu's.

What i mean is ,i would like to have a full always say 750mhz ,is this possible at bootup and throughout use ?

AFAIK all CPUs nowadays do scaling.
Intel only offer two speed rates (half and full) whereas ARM can change the speed on-the-go in MHz without you even noticing.

As said, I might be talking bullshit here, I THINK it's the case, but I'm not really sure

 

[paddy]

Right if all the cpu can do is scale even when overclocked/clocked higher then what is the point ,what is the default ratio of the cpu ? so if it's 500mhz default then how much will the cpu automatic scale to ? or would it underclock as 500mhz is the default ?

I don't understand ,please bare in mind i don't know all the ins n outs of cpu's - so if i use the clock feature and set from default 500mhz to 750mhz overclocked ,the desktop and all apps and infact the clock speed would stay at 500mhz default unless i push the cpu with an application or game ? and that ramp would go to 750mhz ? or only to where the sensor thinks is best ?

I am old school like amd athlon ,can't we just overclock the dam thing and be done with it, 750 all the way ? coz this sounds crap to me.

 

[fusion_power]

@MWeston:
If you switch to 700MHz, nothing will immediately happen.
AFAIK, Linux and the OMAP scales. You set the MAX speed, but as long as the CPU usage isn't too high, the CPU won't clock to 700MHz. At least that's what I think - but I might be in error there .)

Would be cool if it works like this. So we don't have to worry if we set the Pandora to 700MHz. When the normal apps only use the Speed they need, even "global overclocking" shouldn't hurt the Pandora to much.

Now we want to see Craigix "100h mp3 playing".

P.S.: Why does the LCD need that much power? I thought it is a Screen with modern LED Backlight which shouldn't need nealy as much power as an normal Backlight.

 

[Mofokubik]

Right if all the cpu can do is scale even when overclocked/clocked higher then what is the point ,what is the default ratio of the cpu ? so if it's 500mhz default then how much will the cpu automatic scale to ? or would it underclock as 500mhz is the default ?

I don't understand ,please bare in mind i don't know all the ins n outs of cpu's - so if i use the clock feature and set from default 500mhz to 750mhz overclocked ,the desktop and all apps and infact the clock speed would stay at 500mhz default unless i push the cpu with an application or game ? and that ramp would go to 750mhz ? or only to where the sensor thinks is best ?

I am old school like amd athlon ,can't we just overclock the dam thing and be done with it, 750 all the way ? coz this sounds crap to me.

The whole point of scaling the cpu clock speed is to save battery power and keep the temperature down. I don't remember how low the clock can scale, but it's alot less than 500mhz.

Think if you were driving your car, and you were only planning on driving in and around town, there's no need to drive 80mph so your transmission would never use the higher gears and waste gas. This doesn't mean your car can't go 80mph or faster, it means you only use what you need..

 

[WizardStan]

Right if all the cpu can do is scale even when overclocked/clocked higher then what is the point ,what is the default ratio of the cpu ? so if it's 500mhz default then how much will the cpu automatic scale to ? or would it underclock as 500mhz is the default ?

I don't understand ,please bare in mind i don't know all the ins n outs of cpu's - so if i use the clock feature and set from default 500mhz to 750mhz overclocked ,the desktop and all apps and infact the clock speed would stay at 500mhz default unless i push the cpu with an application or game ? and that ramp would go to 750mhz ? or only to where the sensor thinks is best ?

I am old school like amd athlon ,can't we just overclock the dam thing and be done with it, 750 all the way ? coz this sounds crap to me.

That is how it works in theory, yes. The idle process (the process which runs when your computer is otherwise doing nothing, because a CPU can't really do nothing) is supposed to send "hey, I'm doing nothing" commands to the CPU. The CPU then starts slowing down automatically until the "doing nothing" commands are far enough apart. I'm not sure how low it can go, but it is really, really low, like 30Mhz or something like that. Then, if you start another process which takes more CPU, the "doing nothing" commands stop and the CPU starts ramping back up again.
It only goes up to the maximum speed, though, and it requires that the idle process actually send these "doing nothing" commands in order to trigger the slow down. I'm pretty sure it does. If the idle process doesn't send the "doing nothing" commands, it will always run at max speed and just waste power.

So yes, if you can clock your Pandora to 750mhz with no problem, then there should be no reason you can't set the speed to 750 and just leave it. Overclocking is not guaranteed though, so even though you should be able to, don't actually count on it. 500Mhz is what the CPU is rated for at standard voltage, 500 is what OPT will be shipping it with.
There are reasons you might not want to though. A poorly written application might go into it's own do nothing loop when it should be idling, thereby driving the speed back up to full and eating battery that it shouldn't. Overclocking can also decrease the life of the CPU, and some people are worried about that (I'm not, I'm saying some people, these people can keep the clock lower). Finally, just because it is stable almost all the time, like 99.999% of the time at 750Mhz doesn't mean it will always be. You could be playing something for hours, one electron skips a track in just the right way, and the system goes down. 500Mhz is the guaranteed stable point. Whenever you overclock, even if you've been doing it for a while, you risk something breaking down in a way that wouldn't happen at standard clock speeds.
You can totally do it, just be aware that there is a risk (even if it is a tiny) of doing so.

 

[Monk]

http://www.open-pandora.org/ advertises the Pandora as being 600Mhz:

ARM® Cortex™-A8 600Mhz+ CPU running Linux