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Recently installed a new motherboard (ASROCK P4VM890) in an old machine, and the CPU fan is now running at full speed all the time.

I downloaded speedfan, and that is reporting a cpu tem of < 40 degrees, which as I understand it is fine. But the control to reduce fan speed seems to have no effect.

Processor is p4 2.66ghz, it has 1gb RAM and is running Win7

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up vote 2 down vote accepted

Take a look in the BIOS in the PC Health / Monitoring / similar options.

There is usually the ability to control a target temperature and speed when you reach that - or just a maximum speed.

Also, I am guessing that your fan and motherboard have the correct amount of pins - It is possible to miss a pin/have a non intelligent fan which goes at 100% all the time.

If you do not see any options, or it is already set at its lowest, it is possible that when you replaced the motherboard, you did not place enough thermal compound - so you may want to check that.... or it is possible that it is not configurable on your board.

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the cpu fan speed is saying 'N/A' in the bios! Nothing in the H/M section is editable. – Mild Fuzz Mar 13 '11 at 7:51
If it says N/A, it is one of 4 things - Fan isn't variable, fan is damaged, Motherboard doesn't support it, motherboard is damaged... sorry I can't really be more help.... Basically it seems like a communication break down somewhere - the fan is not reporting it's speed, so the motherboard is telling it to go at full speed... just not sure where the problem is! – William Hilsum Mar 13 '11 at 7:56
as the mobo and the fan are new, I could really do with working it out. Any way to work this out? – Mild Fuzz Mar 13 '11 at 8:00
I would say, disconnect your new fan from the board (keep it on the CPU), and plug in your old one if you have it and turn on the system and see if that gets reported. If it does, it means that the new fan is faulty/not reporting its speed. – William Hilsum Mar 13 '11 at 8:01… – Mild Fuzz Mar 13 '11 at 8:01

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