4pin header confusion.

[ShiftyEffect]

I'm trying to figure out if my 4pin system fan headers have PWM control. My gut says no, but I can't find a definite answer online. I have a MSI G45 Z97 motherboard and the manual can be downloaded here (for reference). The fan headers in the manual show the CPUFAN1/2 headers pins 1-4 as Ground, +12V, Sense, Speed Control. The SYSFAN1/2/3 pins 1-4 as Ground, Speed Control, Sense and lastly NC. So the system fan headers don't support 12V for PWM and what is NC? This leads me to believe that the 4pin headers are really 3pin with voltage control.

 

I'm replacing my 3pin static pressure fans on my H110i GTX cooler with PWM fans soon, I was wondering if I could do the same with my other case fans. Any help would be appreciated.

[Grrizz]

NC = Not Connected so the system fans wont support PWM control which is common but they probably still have speed control through voltage regulation.

[Kirky2k15]

NC = Not Connected so the system fans wont support PWM control which is common but they probably still have speed control through voltage regulation.

Oh great, this has got me thinking now, does my z97 MSI Krait edition mobo support PWM? 

[Grrizz]

Oh great, this has got me thinking now, does my z97 MSI Krait edition mobo support PWM?

Its kind of six of one, half a dozen of the other anyway as voltage regulation is usually done through PWM, the only real advantage I can see of having it on the fan itself is that low speed on the motherboard could be under some fans spin up speeds (or over its minimum speed in some cases) while low speed on a fan will be tuned to be within its operating range, which would also make sense as to why they only bother to use it for the CPU fan most of the time while opting for greater compatibility on the, less vital, system fans.

[Kirky2k15]

Its kind of six of one, half a dozen of the other anyway as voltage regulation is usually done through PWM, the only real advantage I can see of having it on the fan itself is that low speed on the motherboard could be under some fans spin up speeds while low speed on a fan will be tuned to be within its operating range, which would also make sense as to why they only bother to use it for the CPU fan most of the time while opting for greater compatibility on the, less vital, system fans.

I'm pretty sure my CPU fan (Hyper 212 EVO) is software controllable and ive done a fan calibration for it so ramp up when temps get hot isn't this what PWM is basically for???

 

CPUFAN1~2,SYSFAN1~3: Fan Power Connectors

The fan power connectors support system cooling fans with +12V. If the motherboard

has a System Hardware Monitor chipset on-board, you must use a specially designed

fan with a speed sensor to take advantage of the CPU fan control. Remember to

connect all system fans. Some system fans may not connect to the motherboard and

will instead connect to the power supply directly. A system fan can be plugged into

any available system fan connector.

[Grrizz]

I'm pretty sure my CPU fan (Hyper 212 EVO) is software controllable and ive done a fan calibration for it so ramp up when temps get hot isn't this what PWM is basically for???

 

CPUFAN1~2,SYSFAN1~3: Fan Power Connectors

The fan power connectors support system cooling fans with +12V. If the motherboard

has a System Hardware Monitor chipset on-board, you must use a specially designed

fan with a speed sensor to take advantage of the CPU fan control. Remember to

connect all system fans. Some system fans may not connect to the motherboard and

will instead connect to the power supply directly. A system fan can be plugged into

any available system fan connector.

PWM fans basically take a pulse in and use the width of that pulse to determine their speed internally through voltage regulation/PWM while standard fans have their 12V input regulated/PWMed by the motherboard to achieve the same thing, the catch being motherboards generally don't have circuits to ID what type of fan is plugged in so plugging a 4 pin PWM fan into either a PWM socket or 3 pin socket will still be speed controllable while a traditional 3 pin fan will only be able to be speed controlled by a 3 pin socket (electrically i.e. the ones with a NC pin if there are 4 pins) and will just run at full speed on a 4 pin PWM socket because the PWM sockets don't have the required circuitry to regulate the 12V rail on the motherboard side.

[Kirky2k15]

PWM fans basically take a pulse in and use the width of that pulse to determine their speed internally through voltage regulation/PWM while standard fans have their 12V input regulated/PWMed by the motherboard to achieve the same thing, the catch being motherboards generally don't have circuits to ID what type of fan is plugged in so plugging a 4 pin PWM fan into either a PWM socket or 3 pin socket will still be speed controllable while a traditional 3 pin fan will only be able to be speed controlled by a 3 pin socket (electrically i.e. the ones with a NC pin if there are 4 pins) and will just run at full speed on a 4 pin PWM socket because the PWM sockets don't have the required circuitry to regulate the 12V rail on the motherboard side.

Wow this is really confusing...

 

The manual for my mobo says CPU fans are

 

1 Ground

2 12V

3 Sense

4 Speed control

 

The Sysfans say

 

1 Ground

2 Speed Control

3 Sense

4 NC

 

Does that mean the CPU fans are PWM and the SYS fans aren't?

[ShiftyEffect]

NC = Not Connected so the system fans wont support PWM control which is common but they probably still have speed control through voltage regulation.

 

Is there a way around this? I haven't used my CPUFAN2 header as both my soon to be replaced SP140 fans on my H110i GTX are on the CPUFAN1. Used in a push config I don't see the need in using 2 more fans for a push/pull setup. Can I use say a 3 way splitter on CPUFAN2 for my 3 system fans? Sounds like a dumb question, I don't think they would be controlled independently from the cooler.

[ShiftyEffect]

Wow this is really confusing...

 

The manual for my mobo says CPU fans are

 

1 Ground

2 12V

3 Sense

4 Speed control

 

The Sysfans say

 

1 Ground

2 Speed Control

3 Sense

4 NC

 

Does that mean the CPU fans are PWM and the SYS fans aren't?

 

It seems so, I don't even know why they are 4-pin, it seems useless. 

[Grrizz]

Wow this is really confusing...

 

The manual for my mobo says CPU fans are

 

1 Ground

2 12V

3 Sense

4 Speed control

 

The Sysfans say

 

1 Ground

2 Speed Control

3 Sense

4 NC

 

Does that mean the CPU fans are PWM and the SYS fans aren't?

Yes but both can still be speed controlled.

CPU:

1 Ground

2 12V

3 Sense

4 Speed control <- Pulses (PWM) tell the fan how much it should regulate its own voltage to ultimately adjust its speed.

Sysfan:

1 Ground

2 Speed Control <- Directly regulates the voltage going to the fan thus adjusting its speed.

3 Sense

4 NC

Plugging a 3 pin fan into the CPU socket means it will only get 12V (pin 2) thus only run at full speed.

Plugging a 4 pin PWM fan into a sysfan socket will cause the fan to default to full speed due to no received PWM signal (pin 4) but still have its speed controlled by the varying voltage provided by the motherboard in the same way a 3 pin fan is controlled (pin 2).

 

Is there a way around this? I haven't used my CPUFAN2 header as both my soon to be replaced SP140 fans on my H110i GTX are on the CPUFAN1. Used in a push config I don't see the need in using 2 more fans for a push/pull setup. Can I use say a 3 way splitter on CPUFAN2 for my 3 system fans? Sounds like a dumb question, I don't think they would be controlled independently from the cooler.

Yes you can use a splitter just be mindful of your current draw, a general rule of thumb is don't exceed 1A per header unless your splitter pulls the power from the PSU directly like:

Alternatively you can still just plug them into the system fan headers as they will still have speed control just in a slightly different way.

[Kirky2k15]

Plugging a 4 pin PWM fan into a sysfan socket will cause the fan to default to full speed due to no received PWM signal (pin 4) but still have its speed controlled by the varying voltage provided by the motherboard in the same way a 3 pin fan is controlled (pin 2).

So does that mean I can use software to control fan speeds if I connected a PWM fan to my Sys fan sockets and set a curve to how I want them to perform? EG the hotter it gets the faster they ramp up? Or can I just get a 3 pin fan and still control speeds with software?

[ShiftyEffect]

Yes you can use a splitter just be mindful of your current draw, a general rule of thumb is don't exceed 1A per header unless your splitter pulls the power from the PSU directly like:

Alternatively you can still just plug them into the system fan headers as they will still have speed control just in a slightly different way.

 

So you're saying I would just need a splitter that uses a molex for power? But wouldn't it run basically as CPU cooler fans do? I would need them to read the system temp and change accordingly wouldn't I? How would that work?

 

BTW thanks for replying, you're very knowledgeable and helpful. This has been my first build so I'm still learning.

[Grrizz]

So does that mean I can use software to control fan speeds if I connected a PWM fan to my Sys fan sockets and set a curve to how I want them to perform? EG the hotter it gets the faster they ramp up? Or can I just get a 3 pin fan and still control speeds with software?

Yes both 4 pin PWM and 3 pin standard fans will be speed controllable on the sysfan headers.

[Kirky2k15]

Yes both 4 pin PWM and 3 pin standard fans will be speed controllable on the sysfan headers.

You probably just saved me some money...

[Grrizz]

So you're saying I would just need a splitter that uses a molex for power? But wouldn't it run basically as CPU cooler fans do? I would need them to read the system temp and change accordingly wouldn't I? How would that work?

 

BTW thanks for replying, you're very knowledgeable and helpful. This has been my first build so I'm still learning.

It depends on your fans if they add up to less than 1A (12W) I would be comfortable putting them on a standard splitter (one motherboard connector to 3 fan connectors), if they add up to more than 1A you will likely want to draw the power from the PSU (or plug the fans into separate headers), you'll note in that picture on the right side there are 3 fan connectors but on the left there is a power supply connector for +12V (yellow) and ground (black) and also a 4 pin fan connector with the sense (green) and PWM (blue) wires to go to the motherboard allowing the fan speeds to be set by the motherboard and one of the fans speeds to be monitored.

[ShiftyEffect]

It depends on your fans if they add up to less than 1A (12W) I would be comfortable putting them on a standard splitter (one motherboard connector to 3 fan connectors), if they add up to more than 1A you will likely want to draw the power from the PSU (or plug the fans into separate headers), you'll note in that picture on the right side there are 3 fan connectors but on the left there is a power supply connector for +12V (yellow) and ground (black) and also a 4 pin fan connector with the sense (green) and PWM (blue) wires to go to the motherboard allowing the fan speeds to be set by the motherboard and one of the fans speeds to be monitored.

 

I understand, I'm not sure what PWM fans I would choose at this time so I don't know the total draw. I can't use PWM fans in my sys fan headers as they can't control with PWM, which is why I asked if I can run PWM fans through the CPUFAN2 header. The only issue is I don't know how they will read my system temp to change speed. It's the CPU fan header to use for more fans on my cooler. I don't see how it would read anything but my cpu/cooler temps. You know what I mean? Not sure if I am articulating this correctly lol.

[Grrizz]

I understand, I'm not sure what PWM fans I would choose at this time so I don't know the total draw. I can't use PWM fans in my sys fan headers as they can't control with PWM, which is why I asked if I can run PWM fans through the CPUFAN2 header. The only issue is I don't know how they will read my system temp to change speed. It's the CPU fan header to use for more fans on my cooler. I don't see how it would read anything but my cpu/cooler temps. You know what I mean? Not sure if I am articulating this correctly lol.

Your PWM fans will still be able to have their speed controlled by the sys fan headers, the amount of control you have is up to the UEFI though. I'm not sure of the level of control your UEFI gives you so if you want to use the system temperature to control your fans you might have to use the sys fan headers and the CPU temperature might only be used for the CPU fan headers, maybe not though, it all depends on how they coded the UEFI but if you do want them controlled by the system temperature and it doesn't let you use that on the CPU fan header you can just use the sys fan headers.

[ShiftyEffect]

Your PWM fans will still be able to have their speed controlled by the sys fan headers, the amount of control you have is up to the UEFI though. I'm not sure of the level of control your UEFI gives you so if you want to use the system temperature to control your fans you might have to use the sys fan headers and the CPU temperature might only be used for the CPU fan headers, maybe not though, it all depends on how they coded the UEFI but if you do want them controlled by the system temperature and it doesn't let you use that on the CPU fan header you can just use the sys fan headers.

 

Well the SYSFAN headers won't allow for PWM control, it would only control through voltage like my 3pin fans that are currently installed. That makes buying PWM fans useless in comparsion to my 3pin fans. The whole point is to have finer control and hopefully lower noise in my case.

 

Not sure how I can find out if the CPUFAN headers allow me to use system temp instead of cpu temp. My motherboard is the MSI G45 Z97. I will have to look through the UEFI to see for that option if it exists. I doubt it does but boy wouldn't that be awesome if it did.