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HP fans use CPU usage instead of temperature?


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I have noticed from day one that my fan speed is varying constantly. Well today I think I figured out why. It looks like instead of using the temperature to adjust the fan speed, they instead have it adjust by processor usage. For example if it goes up to 100% the fan goes to 100%. Then every time it drops off in usage the fan drops and vise versa. My guess would be they did this to cut the cost of having something to monitor the temperature? I have never heard of them using the CPU usage to determine fan speed though lol.

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No its all by temperature, and prediction of temperature.

When the CPU temp. gets higher the fan speeds up. When the CPU usage starts to get higher the fan also speeds up even if the CPU temp isnt getting higher.

It does the same thing on my mac. If i start a flash app, the fan speed gets higher. Even if i start final cut and don't do anything it will get higher.

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For windows based PC all of this is controlled by ACPI..  Many other OSes support ACPI but since you are using Windows we will go with this.  This is basically a table that Windows reads then implements what the manufactures says is on the computer..  This is far different, and has replaced for the most part, any type of full BIOS controlled power management.  What ACPI is basically gives the OS access to the BIOS commands that allows for ultra low-resource power usage. Which is how Centrino works and AMD's Turion works.  The OS is able to control the physical hardware not just the computer.  So if you choose to put your computer into low batter usage it is possible for the OS to turn off a memory stick, speed step the processor and deactivate the wifi.  So it is possible that because your pc jumps to 100% and depending on what power scheme you have the fan ramps up to provide extra cooling.  If you are in a battery saving mode I could see this happening.  Normally your are not gaming in batter save mode so the need for the fan to run is going to be less and add in speedsteping of some sort it is possible that the fan would only turn on when the CPU is maxed.

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maybe it's because CPU's usually heat up when they're at 100% usage...

No I am talking the fan will literally fluctuate constantly. Like it never actually stays at a steady speed. It will fluctuate as much as the CPU usage does.

To swimmer this is a desktop not a laptop. But it is hard to explain just how much my fans speed fluctuates. It will literally change speed every second or 2. It never keeps a steady speed. It sounds really odd.

I can watch my CPU usage meter and the fan is perfectly in sink with the fluctuations of the processor usage. Like if there is a split second drop in usage the fan drops with it.

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