Processor Scaling

[Karl F. Larsen]

Derek Broughton wrote:
> 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.
>>>       
>
> So what you've just said is that you didn't understand a word of what was 
> written...
>
> Did you have a clue what it meant by V^2?
>
> It also points out "modern CPUs are strongly optimized for low power idle 
> states" - and you've yet to provide any evidence that yours _is_ one of 
> those (it's not really even true - the _cutting edge_ cpus, are, but there 
> are still huge numbers of commodity cpus that don't even do frequency 
> scaling).
>
> Absolutely, it's right that voltage scaling is the best way to reduce power 
> consumption - but that doesn't bear any relationship to what either you or I 
> said above.
>
>
>   
    Let me just say my motherboard comes set to over voltage the CPU 
which is expected to get faster CPU speeds. Children are VERY interested 
in this. I am 73 years old and not long ago I got a 10 MHz chip to put 
in place of the regular 1 MHz chip. I raised the speed by 10/1 and it 
was hard to tell! So my 1 GHz chip I know have is so fast it is 
instantaneous.
    So if my speed was cut by 4 it would not be noticed.

Karl

-- 

	Karl F. Larsen, AKA K5DI
	Linux User
	#450462   http://counter.li.org.
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