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Installing a case fan that requires the CPU fan socket?

Last response: in Components
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October 15, 2010 4:00:38 PM

Hello,

I recently purchased a case fan that requires the power from the CPU fan mobo socket (4 pin), it (the case fan) has a connector coming out of it for the CPU. Now, is it safe to do this? To plug the case fan into the CPU fan socket and then the CPU fan wire to to the case fan socket?

I'm monitoring the temps and it seems that the CPU fan doesn't run any higher than 2100 rpm. I'm using the stock cooler for my Q9400.

Should it go any higher than 2100rpm at all?

More about : installing case fan requires cpu fan socket

a b à CPUs
October 15, 2010 4:27:16 PM

Since they're daisy-chained, as long as both fans receive power and running, then it's fine. But if you're really curious. Why don't you do some experiment with the temperature and fan speed with the CPU cooler directly connected to the motherboard, and the second setup with the CPU fan connected through the case fan.
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October 15, 2010 4:45:46 PM

It's really a pain. The socket lies just on top of my video card and the on-board sound input block. If I had smaller fingers, maybe I could be bothered. Besides, I'm more-or-less aware of the temperatures before the switch. Still running at about 39-40 on idle. Yeah, I know.

This, apparently, didn't particularly help the case. My previous back case fan was in-taking, basically the only thing pulling air out was the PSU. Now, this case fan is pulling the air out too. I have a large 120 in the front and 2x 80mm on the side. It's virtually impossible to tell whether the 80mm ones are in-taking or not. How do you tell? They're also the kind that you can't just flip around.

What I'm also wondering is what is the maximum RPM of the stock intel Quad 2 Core fans? I couldn't find anything on Google. I'm guessing if it's 2.2k for iCores, it should be 2.1k for Quads? Which this is running at, on full load.

One of the cores goes up to 72 C on full load, however...
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a b à CPUs
October 15, 2010 5:07:57 PM

Well, that's quite some complex issue you got there. First of all, the rumors around said that Intel's stock fan simply sucks. I'm not the one who said it, check around and you'll see it. Since I already retired my P4 for my AMD Athlon, I'm really in no position to judge that.

There's something you can try to determine the direction of the fan flow. It's quite simple really, so simple it sounds stupid: Stretch a sheet of tissue at the fan's grill. If it's sucked in, well not really, just stuck to the grill, then it's an intake. And the contrary, if it's blown away, it's an exhaust. Simple as that...

As for the idle temperature, that's still within normal. That core at 72 degrees however, is not. What's the temperature on the other cores? Again, due to my lack of knowledge with Intel CPUs, I'll leave this to the others to analyze.

To help us have a better view of your situation, please post the corresponding components which are related to your issue in details.
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a b ) Power supply
a b à CPUs
October 15, 2010 5:09:20 PM

It is OK to connect the fan as intended - the CPU_FAN mobo port can supply enough power for TWO fans, but maybe not more. This is an interesting way to supply a 4-pin Case Fan in a system with no 4-pin ports on the mobo for a Case Fan.

However, it's not really necessary. A 4-pin fan is designed to be provided with a Ground and +12 VDC power supply, a PWM control signal, and a fan speed (output by the fan motor) signal line back to the mobo port. Inside the fan, a small circuit uses the PWM signal to control exactly how much current does flow through the motor to achieve speed control. Such a design is backwards-compatible with 3-pin mobo fan ports. Mechanically you will find that the 4-pin connector on the end of the fan's wires will fit onto a 3-pin mobo port. When done that way, the same Ground, +VDC and Speed signal lines are connected - just the PWM line is left unconnected. Within the mobo's control circuits for a 3-pin fan port, the fan's speed is controlled by reducing the +VDC voltage line to less than 12 V when the fan speed is to be slower. When such a signal is fed to a 4-pin fan with NO PWM signal, it just uses all of that voltage to drive the motor, and it becomes essentially a 3-pin fan motor working just fine.

Connecting it to the CPU_FAN port as it is designed works, with one small exception. The SYS_FAN port on a mobo, intended to control a Case Fan, bases its fan speed control loop on a temperature of the MOBO measured by its own sensor. The CPU fan, on the other hand, has its speed control based on a different temp sensor built into the CPU itself. By using this fan as designed, its speed will be governed by the CPU temp, not by the mobo temp. In practice this is not likely to cause any trouble, especially since OP has other case fans also operating.
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October 15, 2010 9:34:54 PM

Best answer selected by rihokroll.
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a b ) Power supply
a b à CPUs
October 15, 2010 9:57:23 PM

This topic has been closed by Mousemonkey
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