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3 pin cpu fan and a 4 pin mobo - does it "just work" always?

Tags:
  • Components
  • CPUs
  • AMD
  • Rosewill
  • Build
  • Motherboards
  • Speed
Last response: in Components
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November 6, 2013 4:57:24 PM

I've been reading a lot of different stories of people using three pin cpu fans on boards with a 4 pin connector. 99% of the time the reports are that it "just works," notwithstanding the rare reports of someone managing to stick it in the 2-4 pins.

But on one site I read "some PC systems need to detect a CPU fan speed signal or they will automatically shut down" and it got me worried. If I'm reading explanations right, pin 3 detects speed and pin 4 regulates speed.

My question, and its probably a dumb one, is does this mean the motherboard needs to detect speed (which a 3-pin connector will allow) or that it needs to have a signal saying it can regulate speed (the fourth pin).

Just getting ready to start a build with an A10-6800K and a GA-F2A88XM-D3H and my plan was to use an aftermarket cooler with a 3-pin connector (and a speed control knob that goes in a slot on the back), and I want to make sure that there's not some non-trivial chance the motherboard is going to get spooked by this configuration and refuse to work. If it's a problem I can stick with the stock cooler, which is four pin.

More about : pin cpu fan pin mobo work

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November 6, 2013 5:47:22 PM

Most motherboards will not work without a fan speed signal from the CPU fan. Yes, the third pin (yellow wire) on the fan connector is the speed signal, and the fourth pin (on a four pin pwm, not the bigger Molex connector) is fan control.

Your fan should work just fine, as long as the small yellow wire can be plugged in to the motherboard. The motherboard just won't be able to control the fan speed.

Casey
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November 6, 2013 7:03:47 PM

My ASUS M5A97 EVO motherboard will beep at me if I have a 3-pin fan on its 4-pin CPU fan Header. Oddly enough, it won't control the fan by voltage either. But I can still boot, even without a fan plugged into the header.

My A85W Biostar motherboard, on the other hand, is rather indifferent - and it will run fans by either PWM or Voltage without complaint. Strange stuff.
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November 6, 2013 7:07:24 PM

Thanks, the fan's a Rosewill Z1, so the fanspeed gets controlled by a knob that gets stuck in an expansion slot. I'm liking the idea of having direct control, plus even though it's a bit of an old-style cooler it's got good reviews.
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September 10, 2014 9:25:53 AM

cklaubur said:
Most motherboards will not work without a fan speed signal from the CPU fan. Yes, the third pin (yellow wire) on the fan connector is the speed signal, and the fourth pin (on a four pin pwm, not the bigger Molex connector) is fan control.

Your fan should work just fine, as long as the small yellow wire can be plugged in to the motherboard. The motherboard just won't be able to control the fan speed.

Casey


so that means any 3pin fan works ?
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