Do 4 Pin PWM Fan Headers Need PWM Fans to Control Speed?

[Operandi]

I'm looking to build a new system and most of the boards I am looking at now have a 4 pin PWM header for the main system fan. Am I going to need a PWM fan to control the speed on this header?

I was planning on reusing my Lian Li PC6070 which has two 80mm exhaust fans and I'd rather not have to track down 80mm PWM fans.

[BillyBuerger]

Depends on the motherboard. Some can control the fans using either PWM or voltage. I think all the Gigabyte boards I have do this. Default in the BIOS is auto where it detects automatically so that if you plug in a non-PWM fan, it then uses voltage. Although I've also seen a lot of boards where the CPU fan will adjust with temp but then the system fan seems to always run at a lower speed. And different boards have different adjustment options built in. Of course things like Speed Fan can usually override these. What board(s) are you looking at?

[Operandi]

I was looking at this Asus AMD 870.
http://www.newegg.com/Product/Product.a ... 6813131647

I downloaded the manual but it didn't say anything about 3 pin fans on the system header so thats not much of a help. Maybe I'll check out the Gigabyte 870 board, I've had good luck with their boards too.

[danimal]

I'm looking to build a new system and most of the boards I am looking at now have a 4 pin PWM header for the main system fan.

is it the cpu fan? because most mb's don't have more than one pwm-controlled fan header, everything else uses a three-pin connector.

[Operandi]

Of course the CPU fan is PWM (its in the AM3 specification) but so is "System Fan 1".

The odd thing is I downloaded the manual for the Gigabyte 870 board and while sys_fan1 is 4 pins the manual has the 4th pin (the PWM pin) labeled as "reserve" instead of "control" as it is on the CPU fan header. That leads me to believe its not even using PWM to control the fan speed, seems kinda odd.