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Actual Power usage of CPU logic?

Here's a rather technical question. I know for a fact that not all the power gets turned into heat in a CPU- some get is used to "actuate" the logic gates so they change states. Relative to the amount of power going into to a modern processor, how much of it is actually used to run the processor, and how much is lost to the environment as heat?
Any help greatly appreciated,
thanks in advance.
9 answers Last reply Best Answer
More about actual power usage cpu logic
  1. Are you a Mac user per chance ?
  2. No, I am not
  3. Well the numbers will be different for each CPU and environmental and usage parameters.
  4. All "power" that is used turns into heat so this is a semantic detail that both of these terms will be related. If you measure heat you are also measuring Watts used to create that heat, and vice versa.

    This is conservation of energy, otherwise where does the power go? Certainly not to mechanical work or to other forms of energy such as light.

    To answer what I think is your question about efficiency, you can take a look at some of the power charts and compare the Idle power draw versus the peak power draw to get some sense of the energy for overhead of the CPU maintenance versus computational work.
  5. I'm not after an exact value- just roughly as percentage how much of the power put into a CPU gets lost as heat to the environment, how much goes into actually powering logic.
  6. Best answer
    100% of the power into a CPU gets turned into heat. The "heat" and powering logic are one and the same thing.
  7. I think the right term you are looking for is leakage power in a chip.

    Here's an article from anandtech that talks about the subject in simple terms. Google Leakage power for more articles.
    http://www.anandtech.com/show/1611/3
  8. raytseng said:
    All "power" that is used turns into heat so this is a semantic detail that both of these terms will be related. If you measure heat you are also measuring Watts used to create that heat, and vice versa.

    This is conservation of energy, otherwise where does the power go? Certainly not to mechanical work or to other forms of energy such as light.

    To answer what I think is your question about efficiency, you can take a look at some of the power charts and compare the Idle power draw versus the peak power draw to get some sense of the energy for overhead of the CPU maintenance versus computational work.



    Excellent point let me re-phrase the question:
    Roughly how much power is dissipated through impedance (therefore not doing any useful work , in regards to the cpus purpose), relative to the amount power input into a cpu in general?
  9. read above. impedance isn't the right term. leakage current/leakage power is what you're looking for.
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