michaelg at seadreamer.net
Tue Jan 6 20:39:29 UTC 2009
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
>> 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 -
> 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 -
> 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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