# fan speed



## over_my_head (Dec 9, 2011)

This is just a curiosity query. How does the fan speed work? Is it off until a predetermined temperature is reached? Does the speed increase at an elevated temperature? Are these features hardware, OS, or software dependent?

Thanks for your replies.

over_my_head


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## WereBo (Apr 5, 2008)

Hi :wave:

The fans on the CPU are hardware-controlled (BIOS), the GPU is usually software-controlled (graphics-driver), but some can't be 'user-adjusted' and are therefore hardware-controlled.

Having said that though, most motherboard manufacturers supply software to 'tweak' the fans so, technically, the CPU-fan is also software-controlled :laugh:

As to their speed, they depend on where they're connected - The mobo-connected (or graphics-card) speed up as the temperature increases, reaching max speed at the manufacturer's maximum recommended temperature (or slightly below that temp, as a safety-margin)

Case fans can be connected directly to the PSU (fan at permanent max-speed), to the mobo (variable according to which fan-controller pins are used), or via a manual/auto-controller - These are often mounted in a spare drive-bay and can be manually controlled for temperature or noise-volume. Also, the panel-controllers rely on 'thermal-probes' (a sensor on the end of a thin wire) to be attached to various key-points around the mobo, so not quite as accurate as the mobo's built-in sensors.


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## over_my_head (Dec 9, 2011)

WereBo,

Thanks for the explanation. The reason I asked about this is observations I have made about two computers I own (both laptops).

Lenovo B570, i3-2330m @2.2GHz, Win7 HPx64 SP1 installed from an iso (source My Digital River), hyperthreading enabled
Lenovo B575, AMD E450 @ 1.6GHZ, Win7 HPx64 SP1 OEM version, box stock

The B570 is more powerful. If my understanding is correct, it is capable of generating more heat than the B575. However, the fan blows harder on the B575. I observe this by feeling the air on the output vents. Using Speccy as a source for internal temperatures, the B570 runs much warmer (especially under heavy load).

It seems to me that the B570 should have at least as fast, if not a faster fan speed, to control the heat more effectively. When I push the B570, I have to use a laptop riser with a built in fan to keep MOBO and processor temps below 140F. (As viewed in Resource Monitor I have seen all four processor graphs running at 60-80% when running mrt.exe full scan.) The ambient temp is 60F. I have never observed internal temps above 120F on the B575.

Should I be concerned? Do you recommend any action on my part? If so, how do I make necessary changes?

Thanks for your follow up.

over_my_head


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## WereBo (Apr 5, 2008)

Although PCs/laptops become more powerful, they're also getting more efficient with the power-usage and heat dissipation.

Unless you feel confident in opening up your laptops to clean them, the best way to help keep 'em cool is to use a can of compressed-air on 'em. With the laptop off, give several short bursts into the air-intake and exhaust, alternating between them to help break up any 'dust-bunnies' inside, finish off with a blast to the air-intake to clear the last bits out. A stiff(ish) artist's brush or even an old (but clean) toothbrush will help in loosening the dust that often sticks to the grilles.


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## Tyree (May 10, 2009)

Bear in mind that all of the components, no matter how much more efficient they become, are crammed into a very small restricted container made out of poor thermal transferring material.
As well as keeping the air vents clean, try to use the unit elevated to allow more fresh air to the underside.
If you have the dedicated graphics option (Radeon HD 6470M) in the B575, that will add a considerable amount of extra heat.


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