CPU Fan question

[bguile]

Case: RV02-EW, cooler xigmatek gaia sd1283, board will probably be asrock 970 extreme 4. I plan on getting the board next week, its the last part I need.

So I am about to finish my build and I was thinking of getting two blue leds fans to set up a push pull configuration for the cpu cooler, but I can't find any leds fans with 4 pins on them, they all seem to be 3 pin. I already have a 4 pin splitter.

If I want to use PWM coming off the mobo header, they have to be 4 pin right? If I use 3 pin they will just run full speed correct?

Side note: Is it even worth it to do push pull configuration? The chip is just a phenom x4 830, and while I plan on OC it, I doubt I will go past 3.6 (assuming it even goes that far).

Thanks.

 

[Zap]

If I want to use PWM coming off the mobo header, they have to be 4 pin right? If I use 3 pin they will just run full speed correct?

With most boards, yes. Some motherboards are still able to control 3-pin fans through voltage adjustments. IDK if yours can or not.

Side note: Is it even worth it to do push pull configuration?

IMO no, unless the heatsink has really densely packed fins, then maybe.

 

[bguile]

With most boards, yes. Some motherboards are still able to control 3-pin fans through voltage adjustments. IDK if yours can or not.

How can I find out if it will or won't?

 

[Paperdoc]

Your mobo's manual does not give a clear answer to your question, I'm afraid. On p. 12 the diagram shows that it has BOTH 4-pin and 3-pin CPU_FAN ports. But on p. 16, Section 2.2, it appears to indicate that a 3-pin fan on that port will always run a full speed. SOME mobo's can control the speed of 3-pin fans by using a 3-pin control process of varying the +VDC line. Some, however, do not do this and maintain that line at +12 VDC always, as the 4-pin design does. That is especially true of 4-pin ports, but I don;t know what this 3-pin port does. On p.63, Section 3.5, we see that you have the option in BIOS to set the CPU_FAN control mode to Full On or Automatic. What is not clear is whether or not the 3-pin port actually does use 3-pin mode to accomplish fan speed control.

To answer your first question, yes, to use the PWM signal for speed control you must be using a 4-pin fan. The answer to your second question - whether a 3-pin fan's speed can be controlled - is unclear because it depends on whether the mobo will use the standard 3-pin control system or not.

By the way, the 4-pin splitter you have probably will work for a pair of 3-pin fans. The splitter will connect in parallel the lines for Pins 1, 2, and 4. 1 and 2 are Ground and +VDC supplies, and 4 is the PWM signal which your 3-pin fans simply will not use (not even connect to). The Pin 3 line should only be connected to ONE of the two fans, so that only that motor's speed speed pulse signal is sent back to the mobo (not both motors' signals).

 

[bguile]

Your mobo's manual does not give a clear answer to your question, I'm afraid. On p. 12 the diagram shows that it has BOTH 4-pin and 3-pin CPU_FAN ports. But on p. 16, Section 2.2, it appears to indicate that a 3-pin fan on that port will always run a full speed. SOME mobo's can control the speed of 3-pin fans by using a 3-pin control process of varying the +VDC line. Some, however, do not do this and maintain that line at +12 VDC always, as the 4-pin design does. That is especially true of 4-pin ports, but I don;t know what this 3-pin port does. On p.63, Section 3.5, we see that you have the option in BIOS to set the CPU_FAN control mode to Full On or Automatic. What is not clear is whether or not the 3-pin port actually does use 3-pin mode to accomplish fan speed control.

To answer your first question, yes, to use the PWM signal for speed control you must be using a 4-pin fan. The answer to your second question - whether a 3-pin fan's speed can be controlled - is unclear because it depends on whether the mobo will use the standard 3-pin control system or not.

By the way, the 4-pin splitter you have probably will work for a pair of 3-pin fans. The splitter will connect in parallel the lines for Pins 1, 2, and 4. 1 and 2 are Ground and +VDC supplies, and 4 is the PWM signal which your 3-pin fans simply will not use (not even connect to). The Pin 3 line should only be connected to ONE of the two fans, so that only that motor's speed speed pulse signal is sent back to the mobo (not both motors' signals).

Wow, really appreaciate the effort you put into answering my question! :thumbsup:

Since it's unclear as to whether or not it will work, I think I will forget the idea of using led cpu fans and stick with regular fans.

I suppose for lighting the case I would probably be better off with getting some cold cathode tubes instead or maybe a led memory cooler.

Thanks again!