4 Pin PWM System Headers; Do I Need PWM System Fans?

[Operandi]

Alright so I'm getting close to pulling the trigger on building a new system (either Athlon II X4, or Phenom II X6) and putting away the reliable but ancient Athlon 2800+ so I can play some SCII.

I noticed both the Asus and Gigabyte boards (AMD 870) I am looking at have 4 pin PWM system fan headers. Am I going to need to get PWM fans for my case to control their speed? I was planning on reusing my Lian Li PC-6070 so two 80mm exhaust fans.

Link to Asus board.
http://www.newegg.com/Product/Produc...82E16813131647

 

[Zap]

Typically a 3-pin fan will only work at full speed on a 4-pin PWM header. If you were considering spending more money on the fans, have you thought about modernizing and get a new case? Newer cases use 120-140mm fans which give better airflow while being more quiet.

The Lian Li Lancool PC-K7B is currently $83 shipped on Newegg. I'm using one and it is really nice. It comes with two 120mm front (with filters!) and one 120mm rear. The chassis is steel, but the exterior is classic Lian Li black aluminum. The buttons and ports are on top, great for computers sitting on the floor.

Another great choice is the Lian Li PC-7FN, with black exterior and completely in aluminum. It is currently $110 shipped at Newegg. It has a bottom mounted PSU, 8 slot support and uses trays for the HDDs which support 2.5" drives (great for SSDs). It uses a 120mm exhaust and 140mm intake fan. It also has the top ports/buttons. You can get the windowed version for $10 more, and even an all black (insides anodized black) version. The PC-60FN is the same chassis with a different looking front grill.

 

[Operandi]

Yeah, thats kinda what I was thinking, I downloaded the Asus manual and it diddn't say anything about the fan headers in regard to control.

Thing is there isn't anything wrong with my current Lian Li aside from 80mm fans but I think they can handle moderate system I plan to put in. I've been building a lot of systems recently and quite a few of those in Lian Li so I'm fairly familiar with what they have now. I'll consider that option, just didn't want spend that much and retire a otherwise great case.

 

[mindwreck]

pc-6070 is too sexy to retire. it can easily handle the heatload unless you're looking to overclock it and still get lows temps

 

[Operandi]

Yeah, I'd hate to just put it in the closet.....

Also, I downloaded the manual for the Gigabyte 870 board and it lists the 4th (PWM) pin on the system header as "reserve" and "control/12+" on the + voltage pin. That leads to believe that its not even using PWM on the system header. Seems kidna odd.

 

[ehume]

If you choose a Gigabyte board, go into BIOS. On the opening page choose PC Health. Then at the bottom enable smartfan and then set smartfan mode to Voltage instead of Auto or PWM. Now your 4-pin fan header will control by voltage.

I suspect all the other motherboards have this adaptability as well.

 

[Zap]

enable smartfan and then set smartfan mode to Voltage instead of Auto or PWM. Now your 4-pin fan header will control by voltage.

I suspect all the other motherboards have this adaptability as well.

I know for a fact that not all boards can do this. MSI is one example that does not implement voltage control on PWM headers - at least I haven't seen it to be true on several MSI boards that I've tried in socket 775, 1366 and AM2.

 

[mv2devnull]

I do have GA-EP45-DQ6. It has two 4-pin and two 3-pin headers. I have disabled SmartFan in BIOS, so the fans should be at full speed. All fans are 3-pin models, so no PWM.

Both 3-pin headers start their fans instantly on poweron. The other two (cpu and sysfan2) start a bit delayed. The sysfan2 starts and mainly runs at clearly lower rpm than its nominal +12V speed. It might speed up later (but I rather changed connections than waited for it). The pin-layout is different in the manual for the two 4-pins, so it might really mean that the sysfan2 is always under speed-control.

Bottomline: non-PWM CPU 3-pin fan (Noctual) works fine on the 4-pin (PWM-able) header (on Gigabyte board).

 

[MrK6]

If you choose a Gigabyte board, go into BIOS. On the opening page choose PC Health. Then at the bottom enable smartfan and then set smartfan mode to Voltage instead of Auto or PWM. Now your 4-pin fan header will control by voltage.

I suspect all the other motherboards have this adaptability as well.

That's what I do. Attach a 3-pin to the 4-pin and SpeedFan controls it with no problem. Maybe it's just Gigabyte boards though, and if so, gold star for them

 

[Operandi]

Well we'll find out I guess. I went with a Gigabyte 870 board.
http://www.newegg.com/Product/Produc...82E16813128443

I plan on using SpeedFan to control the fans unless the BIOS dose a really job on its own.

 

[ehume]

I do have GA-EP45-DQ6. It has two 4-pin and two 3-pin headers. I have disabled SmartFan in BIOS, so the fans should be at full speed. All fans are 3-pin models, so no PWM.

Both 3-pin headers start their fans instantly on poweron. The other two (cpu and sysfan2) start a bit delayed. The sysfan2 starts and mainly runs at clearly lower rpm than its nominal +12V speed.

I corresponded with Gigabyte tech support on that. The SYS_FAN2 header is for cooling a chipset (for P55 boards it's the PCH). This is independently controlled to respond to the chipset temp. Since the PCH never gets hot the fan speed never goes up. I have gotten the fan speed to go down by blowing air on the PCH though.

The SYS_FAN2 header will convert to voltage control if you set speed control to voltage rather than PWM.