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My PC has:

  • Core 2 Duo
  • 4GB RAM
  • ATI 5450 Radeon graphics
  • Windows 7 64-bit

I want to reduce maximum CPU usage in Power Options in the Control Panel to avoid overheating. Is this safe, or can reducing the maximum CPU usage damage hardware (hard disk, CPU, etc.)?⠀⠀⠀

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  • If your cpu supports this capability, the underclocking it,is perfectly safe. Research if your CPU has this ability. If you have the ability to overclock it you can underclock it. Of course you CPU already does this out of the box. Unlikely you will gain any significant heat reduction by doing this. The Core 2 Duo ran out using stock settings.
    – Ramhound
    Dec 13, 2013 at 16:34
  • I think underclocking is done from BIOS im talking about power options in control panel
    – ali
    Dec 13, 2013 at 16:42
  • It is perfectly safe and will not harm your computer. Also, you can read this: superuser.com/questions/565347/…
    – ruslaniv
    Dec 13, 2013 at 17:01
  • Thank you, but i noticed the screenshots in the link you gave me says "battery", is that article for laptop users? because im on a desktop
    – ali
    Dec 13, 2013 at 17:02
  • @ali - The power options your talking about cannot be used to prevent your cpu from running out. You would need to underclock your CPU to do that.
    – Ramhound
    Dec 13, 2013 at 17:06

1 Answer 1

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The option in question is not under-clocking; Windows does not manipulate the CPU or motherboard or multipliers or FSB or anything. The option you are inquiring about is simply a factor that is used during task-scheduling.

When processes run, the Windows task-scheduler allocates a specific number of CPU cycles to different processes and switches back and forth to enable preemptive multitasking. Normally, it assigns as many CPU cycles as are available in order to run everything as fast as possible. If there are free cycles, it lets the program run, if not, it puts the process in a queue and checks to see if there is another program which has used up its allotment for the current “quantum” (or “time-slice”) and should be moved to the back of the line.

Not surprisingly, running the CPU at 100% capacity for a while will heat it up, and this can be undesirable. What Windows lets you do is to assign a limit to how much CPU capacity is usable.

In this case, when processes request CPU time, the scheduler works exactly as before, except that it uses the limit specified in its calculations instead of 100%. As a result, there will be CPU cycles that remain unused, which allows the CPU to remain at a lower temperature.

As a simplified and contrived example, imagine that this was the pseudo-code for the scheduling algorithm (with comments marked by ;):

; function to calculate total CPU cycles used by all processes
calc-total-used:
  used-total = 0                             ; initialize counter to 0
  for each program:                          ; loop through each running process
    used-total = used-total + process-used   ; add CPU cycles of each process to counter
  return used-total as percentage            ; convert to percent and return value

; main scheduling control, check if free cycles available
if (calc-total-used < max-percent)           ; calc used %, see if less than max allowed
  then run program                           ; if so, run the program
  else:                                      ; if not, try to free some up
    add program to queue                     ; if not, add it to the queue
    …                                        ; check if any process are out of cycles

Notice how the scheduling calculation uses a max-percent variable instead of hard-coding 100%. This way, if you set it lower than 100%, it will only allow a program to run if the current usage is less than 100%, which of course means that any CPU cycles between max-percent above that will not be used.

Therefore, this option cannot harm the CPU; it is no different than simply not running any programs and just idling the system (you have likely already had your system idling near 0% CPU load many times).

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  • @Synetech Does setting processor usage on Windows work the same way as setting it on Ubuntu?
    – Varaquilex
    Dec 16, 2013 at 23:10
  • @Volkanİlbeyli, I’m not sure. Linux isn’t like Windows; that setting actually might manipulate the hardware. Microsoft wouldn’t do that because it would leave them open to potential lawsuits for damaging people’s systems (especially since manipulating the scheduler is a safer, universal option which works perfectly well; manipulating the hardware is system-specific). Linux isn’t a corporation (at least not the Ubuntu distro) and is free, so they have a lot more freedom to do experimental things like over-/under-clocking. You can find out for sure at Ask Unbuntu.
    – Synetech
    Dec 17, 2013 at 1:15

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