Fans connected to psu vs. fans connected to motherboard

[danedude1]

Hey guys. I built my computer in January, and ive never tweaked my 4 (1 back, 2 top, 1 front) case fans in any way. Ive always assumed the fans connected directly to the PSU run at 100%, but i just discovered otherwise. The two fans i have hooked up to my motherboard run very very fast (3k rpm,) and the other 2 fans hooked to the PSU run much slower (400 rpm ish.) First question, are these fans connected to my psu that run very slow doing much? I have no idea how to know when my computer is too hot, etc. Also, i only have 2 ports on my mobo for 'sys fan.' Question two, how do i know what to run my sys fans at, if i do start controlling them? Right now, they are extremely loud, and always have been, so i want to turn them down, but i want to do so safely. Tips? Suggestions? Thanks in advance!
Edit: Also, can i change the speed of the PSU fans without a fan controller addon?

 

[MegaMan1]

Which motherboard? Which PSU? I would have guessed the PSU fans run full speed too.

 

[danedude1]

It is a Biostar T series (TA870U3+) mobo and a Corsair (CX500) PSU.
I came to the conclusion that the case fans connected to the PSU are running slow because i unplugged them, and the computer didn't get much quieter compared to when i unplugged the fans connected to the SYS FAN ports on the mobo.
Edit: Here's a screen cap of my SpeedFan UI. This confuses me. PWM3 changes the speed of my CPU fan, PWM 1 and PWM 2 seeming do nothing. I feel like "automatic fan speed" did nothing as well. http://imgur.com/SX0ls

 

[amuffin]

You should be able to control the fan speeds through your bios and/or through software that biostar provides you.

 

[ngrego]

With 4 fans and only 1 3pin SYS_FAN header you will need a fan controller to to fine tune your fans.
Have you installed the fans with a proper push pull setup?
Also I'm pretty sure that the PSU fans are controlled by the PSU itself, according to the needs of the PSU. You shouldn't be surprised by slow running fans, unless you are OCing they don't need to run high all the time. I have only 2 120mm fans on a MID ATX case and I can barely hear them, although since they are just 2 they have more cooling to do.

 

[danedude1]

With 4 fans and only 1 3pin SYS_FAN header you will need a fan controller to to fine tune your fans.
Have you installed the fans with a proper push pull setup?
Also I'm pretty sure that the PSU fans are controlled by the PSU itself, according to the needs of the PSU. You shouldn't be surprised by slow running fans, unless you are OCing they don't need to run high all the time. I have only 2 120mm fans on a MID ATX case and I can barely hear them, although since they are just 2 they have more cooling to do.

There are two 3 pin SYS_FAN ports on my mobo, just to be more clear. Also, I have one intake fan in the back, and three output fans on the top and front. Is this okay?
Edit: Actually, turn PWM1 down to 0% completely stops my heatsink fan from spinning, while turning PWM3 to 0% make the fan still spin very, very slowly. I seemingly have no control over the two SYS_FANs.

 

[ngrego]

I checked your MOBOs manual out and there should be a Smart Fan Configuration option under "Advanced". If you set that to "Auto" then your mobo will handle all the connected fans as needed. Otherwise you could look through the options and set up the fan control as you see fit.

As for the fan setup in your case, 1 intake fan and 3 exaust fans is the "correct" fan setup but the 1 intake fan is usually in the front of the case. The reason for this is to have a front to back air stream in one direction. Since all of the important components are usually in the back of the case you would want all the heat from those components quickly sucked away from them right out of the case, with the front fan feeding them cooler air from the front of the case.
Also keeping all the cables tied up and pulled to the side allowing the air flow to move as freely as possible through the case will also help for better coolong.