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Poll: Do you think its possible to overclock the N900?!
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Do you think its possible to overclock the N900?!

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MONVMENTVM is offline MONVMENTVM
2010-06-30 , 12:14
Posts: 145 | Thanked: 91 times | Joined on Jun 2010
#4561
Originally Posted by arbitrabbit View Post
Even while playing Music or running a movie, the CPU is not ON all the time. A lot of that is done via the DSP anyways, so your CPU would remain idle a significant amount of time (as an example, play an mp3 and run Conky and you would see that the CPU is usually at 500MHz if you are running ideal). So while the test is valid, the premise isn't. Also, to sample current properly, unfortunately once every second isn't enough. You are talking more like 30 times a second, given how many times the CPU is waking up every second.

Having said that, there is definitely a compromise frequency, which would vary from device to device. So for ideal, it could be 600Mhz but for LV, it could be lower.
One sample per second is enough in this test because I feed the CPU with constant load. The variation between the results usually is maximum +/- 10mA... if i raise the time span from 1 minute to several minutes or even an hour, then the variation should be even less and we should achieve even more precise results (but you still get a good idea from these results).

Polling 30 times a second should basically be no problem but I assume that this alone would possibly create too much CPU load and therefore affect the result.

You are right that while playing music, the CPU stays mainly at 500MHz with ideal configuration, which is because CPU load stays usually around 20 - 30 %. But that wasn't necessarily what I was testing for, as I was setting the frequencies to a fixed value to check WHICH frequency is the most efficient in terms of battery consumption. So I don't really get your point. Besides if you check powertop while playing music you'll see that the CPU never gets into its deepest sleep state C3 (which again is slightly offtopic here).
 
Matan is offline Matan
2010-06-30 , 20:08
Posts: 1,224 | Thanked: 1,763 times | Joined on Jul 2007
#4562
Originally Posted by MONVMENTVM View Post
Clock [MHz]
Time [s] when Pi calculation finished
average current consumption [mA?]

So here it goes:

500
49
556

600
41
560

850
31
609

1000
25
736

My conclusion at the moment though is that a higher clock (even with lowered voltage) isn't necessarily more battery friendly than a lower clock just because it allows the CPU to complete its tasks faster and have more sleep time. This is probably because at higher clocks it consumes so much more power that it's not worth it... anyway I'll also have to check how the CPU behaves at 125MHz and 250MHz... At the moment 600MHz seems to be most effective clock though.
Your data does not support your conclusion:

The CPU took 41*560=22960 units of energy to calculate pi at 600MHz, but only took 25*736=18400 units to do the exact same job at 1000MHz, so was, in fact 20% more power efficient at 1000MHz.
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Matan is offline Matan
2010-06-30 , 20:22
Posts: 1,224 | Thanked: 1,763 times | Joined on Jul 2007
#4563
Originally Posted by arbitrabbit View Post
Even while playing Music or running a movie, the CPU is not ON all the time. A lot of that is done via the DSP anyways, so your CPU would remain idle a significant amount of time (as an example, play an mp3 and run Conky and you would see that the CPU is usually at 500MHz if you are running ideal). So while the test is valid, the premise isn't. Also, to sample current properly, unfortunately once every second isn't enough. You are talking more like 30 times a second, given how many times the CPU is waking up every second.
Assuming you use the BQ27200 to read current consumption (is there another way on the N900?), then you should know it is only updating the value every 5.12 seconds, so there is no use of reading it more frequently. Further more it gives you the average over that time (actual amount of power consumed in the divided by 5.12), so you don't have to worry about that.
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MONVMENTVM is offline MONVMENTVM
2010-06-30 , 22:15
Posts: 145 | Thanked: 91 times | Joined on Jun 2010
#4564
Originally Posted by Matan View Post
Your data does not support your conclusion:

The CPU took 41*560=22960 units of energy to calculate pi at 600MHz, but only took 25*736=18400 units to do the exact same job at 1000MHz, so was, in fact 20% more power efficient at 1000MHz.
Hmm... that's not entirely true. It took 560mA to calculate pi, which finished after 41 seconds, AND to stay in idle mode for another 19 seconds. On the other hand it took 736mA for calculating pi at 1000MHz, which finished after 25 seconds, AND to stay in idle mode for 35 more seconds.

In both cases the test time was 60 seconds. The faster the cpu was, the faster it finished the calculation of pi and therefore was able to spend more time in idle mode until the 60 seconds finished. But as you can see even if it takes less time to finish the calculation and get into idle mode at 1000MHz it's still consuming more power overall.

Edit: But this shouldn't shock anybody... it really would be paradise if we could overclock by almost 100% and save battery at the same time ^^.
Last edited by MONVMENTVM; 2010-06-30 at 22:22.
 
egoshin is offline egoshin
2010-06-30 , 22:55
Posts: 992 | Thanked: 995 times | Joined on Dec 2009 @ California
#4565
Originally Posted by MONVMENTVM View Post
But as you can see even if it takes less time to finish the calculation and get into idle mode at 1000MHz it's still consuming more power overall..
Huh? Idle mode for 3430 is effectively around 20-30 and that mostly depends from VDD2 setup (mSD etc). How did you get your conclusion?
 
MONVMENTVM is offline MONVMENTVM
2010-07-01 , 07:14
Posts: 145 | Thanked: 91 times | Joined on Jun 2010
#4566
Originally Posted by egoshin View Post
Huh? Idle mode for 3430 is effectively around 20-30 and that mostly depends from VDD2 setup (mSD etc). How did you get your conclusion?
I get this conclusion from the results of the measurement!? It's 560mA vs. 736mA... ergo it's easy to understand that it's using more current at 1000MHz.
 
lucas777 is offline lucas777
2010-07-01 , 07:21
Posts: 738 | Thanked: 179 times | Joined on Mar 2010 @ Gold Coast, Australia
#4567
Hey guys serious question here, i just overclocked mine to 500 1100 running super fast and fine atm, im look at conky and its jumping from like 700 to 500 to 1100 whats the go here and i just seen 805.... when i was in terminal i just went sudo...

kernel config limits 500 1100 succesfully loaded

is that normal to see it go from 700 to 500 and random like that.. when im pushing it to it stays at 1100
 
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matts76 is offline matts76
2010-07-01 , 07:42
Posts: 324 | Thanked: 201 times | Joined on Apr 2010 @ UK
#4568
Originally Posted by lucas777 View Post
Hey guys serious question here, i just overclocked mine to 500 1100 running super fast and fine atm, im look at conky and its jumping from like 700 to 500 to 1100 whats the go here and i just seen 805.... when i was in terminal i just went sudo...

kernel config limits 500 1100 succesfully loaded

is that normal to see it go from 700 to 500 and random like that.. when im pushing it to it stays at 1100
Your cpu will use every freq that you haven't avoided, its just that conky cant take frequent enough samples to show all of them.
With ondemand govenor under load it will scale up to your max freq and then scale down through all the available freqs one by one.
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MONVMENTVM is offline MONVMENTVM
2010-07-01 , 07:43
Posts: 145 | Thanked: 91 times | Joined on Jun 2010
#4569
Originally Posted by lucas777 View Post
Hey guys serious question here, i just overclocked mine to 500 1100 running super fast and fine atm, im look at conky and its jumping from like 700 to 500 to 1100 whats the go here and i just seen 805.... when i was in terminal i just went sudo...

kernel config limits 500 1100 succesfully loaded

is that normal to see it go from 700 to 500 and random like that.. when im pushing it to it stays at 1100
Are there any processes running?
 
gsever is offline gsever
2010-07-01 , 07:49
Banned | Posts: 388 | Thanked: 57 times | Joined on Mar 2010
#4570
Originally Posted by matts76 View Post
Your cpu will use every freq that you haven't avoided, its just that conky cant take frequent enough samples to show all of them.
With ondemand govenor under load it will scale up to your max freq and then scale down through all the available freqs one by one.
Ondemand governing is default mode on the CPU, right?
 
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