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when the number of applications running in a pc increases, the power consumed by the PC is also increasing. Is this correct?

I think the reason behind this is CPU. Please let me know what role the CPU plays for more power usage.

Thanks, Kavi

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5 Answers

up vote 2 down vote accepted

If the CPU is idle, it uses less power than when it is being used. Running more programs usually increases the CPU load. However, running one CPU intensive task makes your PC use more power than running several tasks with low CPU usage. Also, disk usage may have much more impact on power consumption than CPU.

As a side note, this question would be better suited on Super User.

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First thanks! But still I got the question Why for "If the CPU is idle, it uses less power than when it is being used." ? Looking for the exact reason behind for this. Is it something like CPU is drawing more power while executing more instructions? –  kumar May 14 '10 at 9:52
    
I have updated my reponse should answer your question –  Yoda May 14 '10 at 10:05
    
The CPU is a CMOS circuit. This means that it only uses energy if a state of a gate is changed, but not when it holds its state. (A CPU has millions of such gates). When the CPU is idle, many of its gates remain in the same state, and when it executes instructions, these gates change state very rapidly. I.e. the power consumption increases, along with heat generation. –  petersohn May 15 '10 at 18:25
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As petersohn said, higher CPU load and disk usage may increase the power consumption of those components. Also, a lot of the hardware components support sleep modes, so if any software is keeping that from happening, that can cause higher power usage. If you are on linux and intel, check out the powertop tool. It will highlight what software is preventing hardware to enter more power efficient states.

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It's easy to believe that the CPU "works harder" when running more processes. But @jackrabbit got it right. There are many things built into modern hardware and into the operating systems to detect when things are idle, and will put the hardware into a low power state (slowing the clock speed, for instance) to conserve power.

Load an OS from the 1980's up and the computer will probably stay at max power, unless the BIOS is smart enough to do the idle thing.

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It's not just the CPU - power consumption for memory, storage and I/O will all increase when there is more activity.

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The way pcs operate is by using electricity, power is pushed through and stored in your components in order to perform calculations and store information so the more calculations you are performing, the more power usage you have.

For example:

  • CPU's operate on charges in transistors
  • Grouped transistors create logic gates which are used to perform your calculations,
  • So when you are using your CPU power is being pushed into the transistors and your usage ramps up.

Equally when "Idle" no calculations are being performed so no power is required to be pushed into the CPU and thus power usage is decreased.

Other components in computers work in similar ways, so the effect is spread across the whole system.

Hope that clears it up a bit more for you.

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The frequency will remain constant, usually CPU's are capable of running above and below there stock running frequency, unless you have a feature called AI Overclocking it will stay the same. –  Yoda May 14 '10 at 10:19
    
Thanks, got it! I have another related question, If a vendor says cpu runnning at 600MHZ, is that mean the cpu is always running at 600 MHZ Or CPU is capable of running at 600 MHZ? This frequency changes with respect to the amount of CPU intensive application or is it a constant one? –  kumar May 14 '10 at 10:21
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