Processor Scaling

[Ray Parrish]

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

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