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3 pins PWM on 4 pins CPU

Last response: in Overclocking
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January 18, 2012 6:44:26 AM

Well, as the title states, I have got two fans in a push-pull configuration on a 212 EVO heatsink, now my problem is that if I connect either of the fans to the 4 pins PWM cpu cooling connector, it starts running at 1700~1900 RPM, while it's supposed to make only 1500 RPM...is this because it's 3 pin PWM? Or is there some other explanation (and solution).
Right now I connected it with a 12 to 7 volt connector to the CPU connector (I don't know how to call it otherwise :p ) and it's running fine, but shouldn't that be a bit too weird?

The pull fan is connected to molex and making less noise than the push fan...

Also, the fans I got are AeroCool Shark Black Edition 12cm and the motherboard is Gigabyte GA-Z68XP-UD3P

More about : pins pwm pins cpu

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January 18, 2012 8:06:05 AM

How are you reading the RPM of the Fan? Via BIOS or software?

Also are you using the 3 pin to 4 pin adapter they include?
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January 18, 2012 8:22:12 AM

Gh0s7y said:
Well, as the title states, I have got two fans in a push-pull configuration on a 212 EVO heatsink, now my problem is that if I connect either of the fans to the 4 pins PWM cpu cooling connector, it starts running at 1700~1900 RPM, while it's supposed to make only 1500 RPM...is this because it's 3 pin PWM? Or is there some other explanation (and solution).
Right now I connected it with a 12 to 7 volt connector to the CPU connector (I don't know how to call it otherwise :p ) and it's running fine, but shouldn't that be a bit too weird?

The pull fan is connected to molex and making less noise than the push fan...

In the BIOS, there is a "smartfan" feature. The name may vary but usually it is set to disable by default. When disable, the BIOS will supply maximum voltage to the CPU FAN so your fan will spin at top speed.
So check in you BIOS & ensure you got "smartfan" or whatever it is called in Gigabyte & enable it.
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January 18, 2012 8:31:16 AM

Reading via BIOS, SMART fan enabled, put on lowest possible voltage/PWM speed, but the fans are still running on max (without the 12 to 7 volt cable). I'll take a picture of it when I can.
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January 18, 2012 8:33:46 AM

The 4th pin is the "control" signal, 3 pin fans have no PWM and are always on. The 12v to 7v adapter would likely cause the fan to spin slower, making it "silence" mode
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January 18, 2012 8:54:52 AM

kinggraves said:
The 4th pin is the "control" signal, 3 pin fans have no PWM and are always on.

Aha...that makes sense, so if I don't have a 4 pin connector for these fans, they're uncontrollable by PWM?
kinggraves said:
The 12v to 7v adapter would likely cause the fan to spin slower, making it "silence" mode

Obviously lol.
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January 19, 2012 9:01:48 AM

Well, I experimented with connections yesterday and I had enough of it so I ordered a fan controller.
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January 19, 2012 1:50:48 PM

If you plug a 3 plug fan into a pwm socket the fan always spins at full power no mater what you set in the bios or in a control software like speed fan.

The difference you see in the RPM of your identical fans is probably because of loose manufacturing standards. A + or - of 10% is typical in fans.

You can get a pwm adapter to turn any fan into a PWM for like 3 bucks on ebay. These are nice because they give you the option to keep using non standard 3 pin fans like the ones in cpu coolers or low pro htpc cases.

I bought and installed 3 of these in my 2 HTPCs and they work great, and you can beat the price. They even work with cool and quite, or smart fan. I just wish there was an american supplier that had them.

http://www.ebay.com/itm/220910624607?ssPageName=STRK:ME...

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January 20, 2012 5:45:35 AM

bucknutty said:
If you plug a 3 plug fan into a pwm socket the fan always spins at full power no mater what you set in the bios or in a control software like speed fan.

The difference you see in the RPM of your identical fans is probably because of loose manufacturing standards. A + or - of 10% is typical in fans.

You can get a pwm adapter to turn any fan into a PWM for like 3 bucks on ebay. These are nice because they give you the option to keep using non standard 3 pin fans like the ones in cpu coolers or low pro htpc cases.

I bought and installed 3 of these in my 2 HTPCs and they work great, and you can beat the price. They even work with cool and quite, or smart fan. I just wish there was an american supplier that had them.

http://www.ebay.com/itm/220910624607?ssPageName=STRK:ME...

Thanks for the explanation there, but from 1500 to 1900 is not 10% more or less...it's almost 1/4 more, is that acceptable?

Also that pwm adapter looks useful I guess. But...shipping worldwide except 50% of all countries lol. Including mine.
Besides I already ordered the fan controller.
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