CPU Fan Speed

[modraker]

I have one computer with an ASUS A7V motherboard and a Duron 700 MHz CPU. It's fan runs at about 7400 RPM. My other computer has an ASUS A7V-E motherboard and a Duron 1 GHz CPU. It's fan runs at about 4600 RPM.

What controls fan speed and why the difference?

[glc]

Different brand and model fans.

[mike breck]

Hi modraker,

Are these different HSFs or the same make and model in both systems?

Some HSF units have a fixed fan speed and you would choose the unit according to how fast a fan you need to keep your CPU cool (or how cool you want it).

Other HSF units, such as the Thermaltake Volcano have a heat sensor and will move to a higher speed when the CPU temp reaches a given temp.

[modraker]

Hello again, glc and mike breck

The heat sinks and fans came with the AMD Duron processors. This is why I'm trying to figure out why they're so different.

[mike breck]

I think I get your drift.

You're wondering why the 1Ghz came with a slower fan and the
700 came with a faster fan. It seems as though it should be the other way round (in fact, I would probably switch the fans around).

Some HSFs will come with a fast, noisy fan to keep the CPU temp down. Other units will go for a trade-off between a lower fan RPM and higher CPU temps because it's less noisy. It depends on the manufacturer and/or supplier who bundles them together.

However, the fact of the matter is you can change the fan on most Heatsinks to achieve your own compromise between temp and noise.

Just out of interest, what are the CPU temps according to the BIOS for both PCs?

[modraker]

Hi mike breck,

You've read my mind. This is exactly what I was attempting to explain.

Do you remember my "unexpected restart" problem? I've solved it temporarily by running my 1GHz computer minus a side panel. The temperature has stayed at 37C since.

I must confess my ignorance about finding the "CPU temp according to the bios".

[piasabird]

The most important fact is the volume of air the fan produces not the rotation speed.

In the USA we use Cubic Feet Per Minute. I don't know what the Metric equivilent is. Maybe it is cubic meters per minute???

[piasabird]

Air flow is another key issue. Hot air has to be evacuated and fresh air has to be supplied. Usually if you can get one or two exhaust fans blowing out fresh air has to rush in from somewhere. Putting a computer in an enclosed area can cause hot air to be recirculated. You might want to compare the temperature inside the case with the temperature of the CPU. Having some sort of vents on the side panels or the top may help to let the hot air out. Hard drives and CDROMS can produce an awful lot of heat inside the case and raise the inside case temp to over 90 degrees F. Soon you are only blowing around hot air and cooling nothing. If you can leave the top slot of a tower open for a fan that might help.