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PRO HELP PLEASE- Case fan into CPU OPT fan slot?

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May 25, 2012 3:48:03 PM

My case has 7 fans and my mother board only has;
4 x Optional Fan connector(s) (4 -pin)
2 x Assistant Fan connector(s) (3 -pin)

I will be getting Molex 4 pin to 3 pin adapters but that leaves one fan that has nowhere to be plugged into except CPU_OPT slot. Will this get the fan going or is that fan going to be left powerless?

Case- http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Motherboard- http://www.newegg.com/Product/Product.aspx?Item=N82E168...
a c 238 V Motherboard
May 25, 2012 4:05:49 PM

I think the CPU_OPT header is an optional one for cpu coolers with two fans. Yes, I think you could plug a fan in there. Would not hurt to try.

If you connect a case fan to a molex psu connector, it will run at full speed.
In the instance of your DF-85 case, there are speed control knobs to reduce the speed for some of the fans.

If you connect a fan with a 3 pin header to a 3 pin header on the motherboard, you get the possibility of controlling the fan speed via some sort of a program such as speedfan.

4 pin headers are likely pwm controlled(pulse width modulation) That is what the stock Intel cpu coolers use. The fan speed is controlled by reducing the frequency of voltage pulsed delivered to the fan.

If you connect a 3 pin fan to a 4 pin pwm header, the fan will just run at full speed.

I do not much like hearing a fan speed constantly changing. I just set it at a suitable noise level and leave it be. It seems to be less obtrusive that way.
If things get a bit hot under load, so be it. Nothing will be damaged.
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May 25, 2012 4:08:59 PM

Keep in mind your PSU will also come with a bunch of Molex connectors, allowing you to connect any 'extra' fans directly to the power supply. I wouldn't connect a case fan to the CPU_OPT header, however, as it's intended for a secondary CPU fan.
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a b V Motherboard
May 25, 2012 4:58:41 PM

If you use the CPU_OPT, would recommend you plug the rear case fan to that. Since that header is tied to the same sensor that drives your CPU fan, the rear fan will spin up at a rate proportional to the CPU cooler.

So, the warmer the CPU, the faster its fan goes, the faster the fan directly behind it pumps the added heat out of the case.

Mine is like that and so far, so good.
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May 25, 2012 9:15:03 PM

Thanks, for all the answers. I actually learned a lot, mostly from the guy that told me you can connect fans directly to power supply :o  I didn't know that, thanks. And I will be getting a fan controller after finding out such thing exists :D  Thanks everybody.
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May 25, 2012 9:16:25 PM

Best answer selected by Gumienny22.
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a c 328 V Motherboard
May 26, 2012 2:21:22 AM

This topic has been closed by Nikorr
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