Question Does my MOBO (auss h270f strix) support pwm fans?

Oct 10, 2020
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I am planning to buy 2 12v scythe kaze flex pwm 120mm fans, but I took a momento to take a look at my MOBO manual about it's fan headers.

According to this print screen I took from the manual: https://prnt.sc/uws3nr. The CHA_FAN headers have a +5V pin. I don't know what +5v pin means, I want to know if I can Install 12v pwm fans on the CHA_FANS 1 and 2 ( they are 4 pins headers, but after some googling, i couldn't find any conclusive answer).

TLDR: I need help to know if my mobo supports 12v PWM fans.
 

jasonf2

Honorable
Oct 11, 2015
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4 wire = pwm, 3 wire = voltage. Looking at that pic you have 4 wire headers so yes you have pwm. That 5 volt you are looking at is the PWM signal. The fan power is going to be 12 volt even though not indicated. If you don't have enough headers to drive your fans buy a hub, not a splitter. Something like this. https://www.amazon.com/Thermaltake-Commander-Powered-4-Pin-AC-023-AN1NAN-A1/dp/B01G9BEC5W/ref=sr_1_5?dchild=1&keywords=pwm+fan+hub&qid=1602634655&sr=8-5 I cannot pull anything on that artic, but if it has an input and a separate power input it is probably fine too as it is being labeled as a hub.
 
Last edited:

Paperdoc

Glorious
Ambassador
Yes, your mobo can use either 3-pin Voltage Control Mode fans or the new 4-pin PWM fans. The diagram you showed does not make that clear, but the details of how to adjust each fan header on p. 3-28 do.

Maybe this can help. A 4-pin fan header might be used for either type of fan, depending on what signals it sends out. Your mobo can be adjusted for either type. When it is set to use PWM Mode, the fan header puts out a constant 12 VDC power supply on Pin #2 and Ground is Pin #1. Pin #3 carries the fan's speed signal back to the mobo. Pin #4 has the PWM signal for the PWM fan, and it is a special type of square wave with the "% On" varying, and a peak-to-peak (On-to-Off) voltage of 5 VDC. That is what the label "5V" means. The PWM fan has a special chip inside it that uses that PWM signal to modify the flow of current from the fixed 12 VDC supply line through the windings to change the fan speed.

If the header is configured instead to use the older Voltage Control Mode (aka DC Mode), it usually sends nothing out on Pin #4, but it also changes what is done on Pin #2. The voltage on that pin is varied from 12 VDC (full speed) down to about 5 VDC (minimum to avoid fan stalling). That is how the speed of a 3-pin fan is controlled. The 3-pin fan does not even connect to Pin #4 because it has no special chip and cannot use the PWM signal.

So, referring to your mobo manual p. 3-18, you can ensure that EACH fan header you use for a PWM 4-pin fan has its Chassis Fan QFan Control item set to PWM, and not Auto or DC. Also, for those CHA_FAN headers you use for the case ventilation fans, change the item Chassis Fan QFan Source to Motherboard. This makes their control based on a temperature sensor on the mobo, rather than on the one inside the CPU chip.
 
Reactions: anotherhardwarenoob
Oct 10, 2020
7
0
10
0
Yes, your mobo can use either 3-pin Voltage Control Mode fans or the new 4-pin PWM fans. The diagram you showed does not make that clear, but the details of how to adjust each fan header on p. 3-28 do.

Maybe this can help. A 4-pin fan header might be used for either type of fan, depending on what signals it sends out. Your mobo can be adjusted for either type. When it is set to use PWM Mode, the fan header puts out a constant 12 VDC power supply on Pin #2 and Ground is Pin #1. Pin #3 carries the fan's speed signal back to the mobo. Pin #4 has the PWM signal for the PWM fan, and it is a special type of square wave with the "% On" varying, and a peak-to-peak (On-to-Off) voltage of 5 VDC. That is what the label "5V" means. The PWM fan has a special chip inside it that uses that PWM signal to modify the flow of current from the fixed 12 VDC supply line through the windings to change the fan speed.

If the header is configured instead to use the older Voltage Control Mode (aka DC Mode), it usually sends nothing out on Pin #4, but it also changes what is done on Pin #2. The voltage on that pin is varied from 12 VDC (full speed) down to about 5 VDC (minimum to avoid fan stalling). That is how the speed of a 3-pin fan is controlled. The 3-pin fan does not even connect to Pin #4 because it has no special chip and cannot use the PWM signal.

So, referring to your mobo manual p. 3-18, you can ensure that EACH fan header you use for a PWM 4-pin fan has its Chassis Fan QFan Control item set to PWM, and not Auto or DC. Also, for those CHA_FAN headers you use for the case ventilation fans, change the item Chassis Fan QFan Source to Motherboard. This makes their control based on a temperature sensor on the mobo, rather than on the one inside the CPU chip.
Thanks for the answer, very detailed. Tks!
 

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