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I have a ASROCK P4VM890 motherboard, which doesn't have controls for variable fan speeds. I was wondering if there are any options available to me, as having the fan running at full speed is not ideal at all.

I have tried to use software within the operating system (win7) but it has no effect, I assume this is because the software can only control fan speeds if the BIOS will allow it to.

Is open source BIOS an option at all?

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up vote 2 down vote accepted

It is unusual for a modern motherboard to lack this functionality, so a couple of things to check:

1) Is the fan you are using the correct type?

For a fan to have its speed controlled it should report its current speed back to the motherboard by means of (usually) an induction sensor. This requires a third wire from the fan back to the motherboard. Check that the fan you are using has three wires and not two (some cheap ones don't have the sensor and thus only 2 wires).

2) Check the ACPI settings of the motherboard.

ACPI stands for Advanced Configuration and Power Interface and is the standard method for controlling and measuring such things as CPU temperatures, fan speeds, battery charge, etc. If ACPI is disabled in the BIOS it may well stop you from using the ACPI facilities.

Failing that, without feedback from the motherboard as to the temperature of the CPU, or some other way of knowing the temperature of the CPU and using that to vary the speed of the CPU fan it would be unsafe to slow down the speed of the fan as at times of heavy load there is a risk of the CPU overheating.

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In my bios I can see the temperature of the CPU, the temperature of the motherboard and the speed of both a chassis and cpu fan (I only have a CPU fan at present). But I can not find any way to control it. – Mild Fuzz Mar 14 '11 at 11:42

Some manufacturers sell fans whose speed varies either according to a thermistor (temperature) or the position of a knob (manual).

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I have seen the manual ones, I am not keen on this solution. I can't find an example of the first option. – Mild Fuzz Mar 14 '11 at 11:43

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