Question PC PWM fan upgrade

Oct 16, 2019
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Hi there,

I'm upgrading my PC 's fans. I want to go with some Noctua A12 PWM fans. My motherboard is a Gigabyte Z97 D3H. Whilst it has 4 pin support, I've heard from some people that it runs fans on full speeds. So can I get a cable splitter and run the CPU fan and the rear case fan off the CPU fan 4 pin?

Also should I replace the front fan? The case I'm getting is the corsair spec 06,

Thanks
 
Oct 16, 2019
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Pick up a PWM fan hub, like one made by Phanteks(and other brands) and pair that with your CPU fan so you have all fans ramp up and swansong down with the CPU's temps.
I really don't have the money to be buying out a dedicated hub, can't I just run the CPU fan and the rear fan of one controller
 

digitalgriffin

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Hi there,

I'm upgrading my PC 's fans. I want to go with some Noctua A12 PWM fans. My motherboard is a Gigabyte Z97 D3H. Whilst it has 4 pin support, I've heard from some people that it runs fans on full speeds. So can I get a cable splitter and run the CPU fan and the rear case fan off the CPU fan 4 pin?

Also should I replace the front fan? The case I'm getting is the corsair spec 06,

Thanks
I would personally go to the gigabyte forum. But off the cuff, I would say there's an adjustment in the BIOS to modulate fan speed if there is a MB header for it.
 
Oct 16, 2019
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I would personally go to the gigabyte forum. But off the cuff, I would say there's an adjustment in the BIOS to modulate fan speed if there is a MB header for it.
So there are options in my motherboard BIOS to control the fan speed. Right now I've got a two three pin fans but i change them to silent in the BIOS and they do not change - presumably because it is a 3 pin?
 

digitalgriffin

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So there are options in my motherboard BIOS to control the fan speed. Right now I've got a two three pin fans but i change them to silent in the BIOS and they do not change - presumably because it is a 3 pin?
I would say so. The only way to control 3 pin fans is via Voltage Modulation.

PWM is always 100% voltage on pin 2. The #4 pin leads to a base of a transistor and pulses on and off allowing the voltage to carry through the motor. PWM is superior because you get a finer grain of control on low speed when you pulse the motor at full voltage (12V)



Some motherboards come with an auto-tune which will automatically switch between PWM and Variable Voltage Control.
 
Oct 16, 2019
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I would say so. The only way to control 3 pin fans is via Voltage Modulation.

PWM is always 100% voltage on pin 2. The #4 pin leads to a base of a transistor and pulses on and off allowing the voltage to carry through the motor. PWM is superior because you get a finer grain of control on low speed when you pulse the motor at full voltage (12V)



Some motherboards come with an auto-tune which will automatically switch between PWM and Variable Voltage Control.
I've heard that the CPU fan is the only PWM 4 pin on the board ( there is another 4 pin but don't believe PWM is enabled on it for some reason). Can I use a splitter and run the case fan and the CPU fan of that? Or will they both max out due to the CPU fan
 

digitalgriffin

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I've heard that the CPU fan is the only PWM 4 pin on the board ( there is another 4 pin but don't believe PWM is enabled on it for some reason). Can I use a splitter and run the case fan and the CPU fan of that? Or will they both max out due to the CPU fan
That 2nd 4 pin fan header may be variable voltage control and ignores pin 4. But it's hard to say. I had an older ASUS Sabertooth Z77 MB that did this.

To answer your question: Yes, a fan splitter off the CPU fan header will do the job. When you buy the fan splitter two connectors should have 4 wires, and one connector should have 3 wires connected to it. One of the sockets on the second header remains unconnected. This is the RPM sense pin. You don't want both fans reporting RPM as that would give inaccurate results. Most fan splitters are built correctly. But I received some off Amazon that weren't. They connected all 4 pins on both!
 
Oct 16, 2019
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That 2nd 4 pin fan header may be variable voltage control and ignores pin 4. But it's hard to say. I had an older ASUS Sabertooth Z77 MB that did this.

To answer your question: Yes, a fan splitter off the CPU fan header will do the job. When you buy the fan splitter two connectors should have 4 wires, and one connector should have 3 wires connected to it. One of the sockets on the second header remains unconnected. This is the RPM sense pin. You don't want both fans reporting RPM as that would give inaccurate results. Most fan splitters are built correctly. But I received some off Amazon that weren't. They connected all 4 pins on both!
Would this one do the job https://www.amazon.co.uk/Splitter-Computer-Converter-Sleeved-Braided-Black/dp/B01N1Z3FYD/ref=sr_1_3?keywords=fan+splitter&qid=1571333390&sr=8-3
 
Let's clarify first what fan speed controls can be done. There are two basic types of fans: 3-pin and 4-pin. The older 3-pin fans can have their speed controlled ONLY if the mobo header uses the older Voltage Control Mode (aka DC Mode), in which the voltage supply to the fan on Pin #2 varies from 12 VDC (max speed) down to about 5 VDC. Any lower and the fan may stall. The newer 4-pin (PWM) fans are designed to receive a constant 12 VDC power supply from Pin #2 and then the new PWM control signal from Pin #4. Inside the fan case there's a small chip that uses the PWM signal to modify the flow of current from that fixed 12 VDC supply line through the motor windings to change the speed. If you connect a fan to its intended supply - that is, a mobo header using either DC Mode for a 3-pin fan, or PWM Mode for a 4-pin fan), you get full speed control. If you mis-match, you get control in one case but not the other. A 3-pin fan connected to a header using PWM Mode will always run full speed because it gets a constant 12 VDC supply from Pin #2 and can NOT vary its own current flow. But a 4-pin fan connected to a header using DC Mode WILL have its speed controlled. Although it does not receive the PWM signal from Pin #4 for its modification chip to use, what it gets from Pin #2 is a voltage that VARIES, and thus its speed IS under mobo control.

OP, the manual of that mobo indicates that its SYS_FAN headers (there are three of them) use only the older DC Mode, but that may not be correct. Sometimes the labels in those manuals are unclear. However, you plan to add 4-pin PWM design fans from Noctua, and as I said above that design CAN have its speed controlled by EITHER type of mobo header, irrespective of the number of pins on the header. So for those fans you will have no problem. For the two fans included in the Corsair Spec06 case it is not so clear. The website for that case does not specify what fan types it includes , but there are two of them. IF they also are 4-pin PWM style fans, then the same applies to them as to the Notcuas - it does not matter which type of mobo header you plug them into. IF they are 3-pin fans, then your mobo headers still MAY be able to control their speeds. It depends whether the manual indication is correct that the SYS_FAN headers all use the older DC mode. If that is correct, then they CAN control the speed of 3-pin fans also.

Given that, where to connect? Recognize that the CPU_FAN and CPU_OPT headers both will use a temperature sensor inside the CPU chip to guide their automatic control actions, so those are where you connect cooling devices for the CPU chip. But the three SYS_FAN headers all use a different temperature sensor on the mobo for guidance, so that is where you plug in case ventilation fans. You have three of those headers, and five fans to connect to them. To start, get a couple of very simple 4-pin SPLITTERS like this

https://www.newegg.com/p/N82E16812423163?Description=coboc fan splitter&cm_re=coboc_fan_splitter-_-12-423-163-_-Product

These have three outputs each, so connecting five fans to three SYS_FAN headers will be easy. NOTE that these devices have a single input connection to a mobo SYS_FAN header and three outputs for fans, and NO other "arms". Do not get a HUB, which is a different type of device that has a third type of "arm" that must plug into a SATA or 4-pin Molex power output connector from the PSU. You don't need that, and a Hub can NOT control the speed of 3-pin fans.
 
Oct 16, 2019
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Let's clarify first what fan speed controls can be done. There are two basic types of fans: 3-pin and 4-pin. The older 3-pin fans can have their speed controlled ONLY if the mobo header uses the older Voltage Control Mode (aka DC Mode), in which the voltage supply to the fan on Pin #2 varies from 12 VDC (max speed) down to about 5 VDC. Any lower and the fan may stall. The newer 4-pin (PWM) fans are designed to receive a constant 12 VDC power supply from Pin #2 and then the new PWM control signal from Pin #4. Inside the fan case there's a small chip that uses the PWM signal to modify the flow of current from that fixed 12 VDC supply line through the motor windings to change the speed. If you connect a fan to its intended supply - that is, a mobo header using either DC Mode for a 3-pin fan, or PWM Mode for a 4-pin fan), you get full speed control. If you mis-match, you get control in one case but not the other. A 3-pin fan connected to a header using PWM Mode will always run full speed because it gets a constant 12 VDC supply from Pin #2 and can NOT vary its own current flow. But a 4-pin fan connected to a header using DC Mode WILL have its speed controlled. Although it does not receive the PWM signal from Pin #4 for its modification chip to use, what it gets from Pin #2 is a voltage that VARIES, and thus its speed IS under mobo control.

OP, the manual of that mobo indicates that its SYS_FAN headers (there are three of them) use only the older DC Mode, but that may not be correct. Sometimes the labels in those manuals are unclear. However, you plan to add 4-pin PWM design fans from Noctua, and as I said above that design CAN have its speed controlled by EITHER type of mobo header, irrespective of the number of pins on the header. So for those fans you will have no problem. For the two fans included in the Corsair Spec06 case it is not so clear. The website for that case does not specify what fan types it includes , but there are two of them. IF they also are 4-pin PWM style fans, then the same applies to them as to the Notcuas - it does not matter which type of mobo header you plug them into. IF they are 3-pin fans, then your mobo headers still MAY be able to control their speeds. It depends whether the manual indication is correct that the SYS_FAN headers all use the older DC mode. If that is correct, then they CAN control the speed of 3-pin fans also.

Given that, where to connect? Recognize that the CPU_FAN and CPU_OPT headers both will use a temperature sensor inside the CPU chip to guide their automatic control actions, so those are where you connect cooling devices for the CPU chip. But the three SYS_FAN headers all use a different temperature sensor on the mobo for guidance, so that is where you plug in case ventilation fans. You have three of those headers, and five fans to connect to them. To start, get a couple of very simple 4-pin SPLITTERS like this

https://www.newegg.com/p/N82E16812423163?Description=coboc fan splitter&cm_re=coboc_fan_splitter--12-423-163--Product

These have three outputs each, so connecting five fans to three SYS_FAN headers will be easy. NOTE that these devices have a single input connection to a mobo SYS_FAN header and three outputs for fans, and NO other "arms". Do not get a HUB, which is a different type of device that has a third type of "arm" that must plug into a SATA or 4-pin Molex power output connector from the PSU. You don't need that, and a Hub can NOT control the speed of 3-pin fans.
Right, I'm confused. Can I just connect the Noctua to the Sys fan header then? If that 's the case surely I won't need a splitter. I'm only using one noctua for now, I plan on just keeping the front stock corsair fan.

It's just a thread on this site had someone with this problem where they ended up using a splitter for the CPU as that was the only pwm.
 
Of you are trying to connect a new 4-pin (PWM style) fan the IDEAL way to control it is for the mobo header to use the new PWM Mode. However, all 4-pin fans are designed with a backwards compatibility feature. If you plug them into a mobo fan header that is using the older Voltage Control Mode (which I believe all of your SYS_FAN headers do) they WILL have their speed controlled by this Mode. So do not worry about whether the header is PWM able. Just go ahead and use the SYS_)FAN header.
 

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