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Quieting CPU fan

I just had my mother board replaced (P4, 3 GHz). The old "HP" board's fan was very, very quiet.

Although the tech said he used the same fan on the replacement board, it now sounds like a hair dryer! He said just buy a quieter fan.

First, why would the same fan be so much noisier?

I read the article in PC Magazine about "Quieting Your PC," downloaded the program "SpeedFan," and installed it.

I think I followed the steps correctly. I can monitor the fans speeds (3 fans) and the CPU temp, plus two other system temps (whatever they are), but the program does not seem to be controlling the CPU fan speed.

SpeedFan is supposed to start at bootup, but I don't think it is. How do I get that program to run at bootup?

System info: Pentium 4, 3 GHz, Hyperthreading, Mother Board is a FOXCONN 661 (SIS-661) with Phoenix BIOS LTD6.00. CPU temp after a few hours is 24 degrees C, and fan speed is 4400 ROM.

In the User Manual there is a diagram of the fan plug pinout. It just shows "Gnd," "12V," and "Sense." Does that mean that there is no control, and that the fan runs at full speed all the time?

Is there a chance that I can control fan speed, or should I just try to buy a quieter fan?

Thanks in advance,


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Re one answer. The fan plug pinout;

In reply to: Quieting CPU fan

"12V" is actually a modulated "square/rectangular" wave whose duty cycle is determined by the sense leads input telling if more [or less] cooling is needed. More cooling needed the on time of the 12 volt gets longer each cycle.

I know nothing about how speed fan provides its control of a number of fans.

IF the temp you are reading, is valid you are in great shape and could cut the CPU's HSF fan speed quite a way down.

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In reply to: Quieting CPU fan

If my CPU ran at 24

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Quiet Fan

In reply to: 24

Thanks, gents. OK, I guess the 12 volts is pulse-width modulated - makes sense.

And, yes, if the 25C figure is correct I'm impressed. But I am suspicious.

Any idea how to ensure that the program starts at bootup?

Thanks again,


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You need to be suspicious of that temp reading

In reply to: Quiet Fan

That makes it about 75 F. For this to be true, your ambiant (room) temperature would need to be in the area of 50 F or less. Something isn't being reported properly, me thinks.

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In reply to: You need to be suspicious of that temp reading

Hi If you find out what is causing your CPU to run at that temp, patent it.
If indeed the tec did install your old fan that ran quietly your noise could be caused by mounting resonance. If you can, dismount the fan and let it run free to see if the noise is still there.If your tec meant the fan was the same MODEL as your old fan then chances are you got a dud fan. Stewart

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Quieting CPU fan

In reply to: Quieting CPU fan

Question. Some HP and most Dell's do not have a fan on the heatsink, they have a case fan with a plastic air duct to force the air over the heat sink, is yours like this? IF so the old MB may have controled the fan speed
and the new MB does not or it is a BIOS setting. If it dosen't cortroll the fan speed the fan will run full speed and be loud. John

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In reply to: Quieting CPU fan

Thanks again for the thoughtful replies.

I do remain suspicious about the reported cpu temp. This morning, after the computer was off all night and, therefore, at room temperature, the temp was reported to be 18 C (64.4 F). That's several degrees cooler than the room was (I'm guessing 22 C). If the offset is constant, then the cpu is still pretty cool, but who knows if the sensor is linear, etc.

The tech said that it is the same fan that he removed. It has a heat sink.

I am thinking now that the old mother board had provision for controlling the fan speed according to temperature. The new one doesn't seem to have that capability. I'm pretty sure that what i'm hearing is due to fanblade tip speed, not vibration.

I guess I'll try a fan with thermistor-controlled speed.

Or, I guess I'll just have to get used to working around turbine engines!

Thanks for the feedback, again.

Enjoy the Fourth.


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