Processor Scaling

[Michael]

Ray Parrish wrote:
> Derek Broughton wrote:
>   
>> Ray Parrish wrote:
>>
>>   
>>     
>>> Well, as I said above I'm not worried about the extra power the "cpu"
>>> not the whole desktop takes... The cpu is just a small chip inside the
>>> box, and runs on 5 volts. Reading comprehension my friend...
>>>     
>>>       
>> Electricity comprehension my friend.  5V or 500V is (largely) irrelevant - 
>> it's the power, not the voltage.
>>
>>
>>   
>>     
> Ok, I did some research, and this supports my view [From Wikipedia]
>
>   
>> Dynamic frequency scaling reduces the number of instructions a 
>> processor can issue in a given amount of time, thus reducing 
>> performance. Hence, it is generally used when the workload is not 
>> CPU-bound.
>>
>> Dynamic frequency scaling by itself is rarely worthwhile as a way to 
>> conserve switching power. Saving the most power requires dynamic 
>> voltage scaling too, because of the V^2 component and the fact that 
>> modern CPUs are strongly optimized for low power idle states. In most 
>> constant-voltage cases it is more efficient to run briefly at peak 
>> speed and stay in a deep idle state for longer (called "race to 
>> idle"), than it is to run at a reduced clock rate for a long time and 
>> only stay briefly in a light idle state. However, reducing voltage 
>> along with clock rate can change those tradeoffs.
>>
>>     
> Article url below -
>
> <http://en.wikipedia.org/wiki/Dynamic_frequency_scaling>
>
> However, it uses more power than I thought as shown in the following quote -
>
> "Sempron 3400+ has a die size of 84mm^2 , produced on AMD's 90-nanometer 
> silicon-on-insulator (SOI) process. It runs at 2.0GHz and features a 
> 256KB L2 cache, and its max thermal power is 62 watts. "
>
>  From the following page -
>
> <http://www.extremetech.com/article2/0,2845,1841866,00.asp>
>
> So, although I'm not really using more power by setting my cpu scaling 
> to Performance, it still uses more power than I thought.
>
> Later, Ray Parrish
>
>   
 From another viewpoint:  My situation requires my computer to be inside 
an enclosed space without a great deal of ventilation.  With scaling my 
cpu runs at 1.3 ghz and about 48 degrees C and the gpu is 58.  At full 
speed the temperature of the cpu raises to about 58 degrees.  If I go to 
windows and play something like Crysis or Fallout 3 I have to keep the 
cabinet door open to prevent the computer from crashing.  I can't check 
the speed or temp very easily but when I reboot to Ubuntu the cpu is 
running over 60 degrees and the gpu is over 65 degrees.  Also everything 
is running from batteries so power matters to me. 


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