Can PWM Fan Control Mode Control DC Fan?

[PeacefulTech]

Hi guys,

Although my mobo can switch between PWM/DC fan control mode, it cannot do so between fans connected to the CPU_FAN and CPU_OPT header. In other words, either both of these fans are controlled by PWM mode, or both are controlled by DC mode.

I have a PWM fan connected to CPU_FAN and a DC fan connected to CPU_OPT. I was wondering whether any fan control to the DC can would occur if I select the fan control mode to be PWM.

I also wonder what would be the optimal fan control profile I should set here? Should I should DC or PWM?

Thank you!

 

[maxfly]

DC fans cant be controlled via pwm.
Its up to you as to which option to go with. I would go with pwm on the cpu fan simply for convenience. But again its your rig and your fans so ...the easiest route would be to pick the best heatsink fan of the two and call it a day. If you find that you still need that last little bit of cooling. You can always buy another fan to match what you have and avoid this conundrum in the future

 

[cvaldes]

The primary usage case of the CPU_OPT header is to provide redundancy for a CPU cooling loop with 2 or more fans (whether it be a liquid cooled AIO loop or a 2-fan air cooler). Thus if the fan attached to the CPU_FAN header fails or if the header itself fails, the fan(s) attached to the CPU_OPT header continue to spin. It works in lieu of a 4-pin Y-splitter fan cable which could also fail.

In the owner's manual of the ASUS ROG Strix B550-E, the illustration clearly shows two AIO fan cables going to the separate headers: one fan cable to CPU_FAN and the other to CPU_OPT.

Your best approach would be to move the DC fan(s) to another header or to buy PWM fan(s) for the CPU_OPT header.

 

[Mussels]

Are they PWM fans? use PWM control
Are they 3 pin fans? use voltage

Some headers can do both, and some PWM fans work well with voltage control... but it's best to use 4 pin fans with PWM, if possible.

 

[eidairaman1]

Are they PWM fans? use PWM control
Are they 3 pin fans? use voltage

Some headers can do both, and some PWM fans work well with voltage control... but it's best to use 4 pin fans with PWM, if possible.

I think all fan headers can do both, just need to connect to correct pins on fan headers.

 

[Mussels]

I think all fan headers can do both, just need to connect to correct pins on fan headers.

i've seen specific mobos that had zero voltage control on specific ports, it happens. Also have a fan controller that only outputs PWM, despite having a voltage in option.

 

[cvaldes]

But that's not OP's problem. OP clearly stated that their motherboard can switch between PWM and DC. The problem is OP has a combination of PWM and DC fans and OP's motherboard CPU_OPT header is tied directly to the communication method used by the CPU_FAN header. This is very, very common.

The OP's three main options are A.) to control the CPU_FAN and CPU_OPT fans with DC (since PWM fans can always be DC controlled), B.) to replace the DC fan(s) with PWM fan(s), or C.) move the DC fan to a different motherboard header.

The OP neglected to mention whether or not an spare fan header was available. OP also didn't bother to say whether or not they had budget for a PWM fan for the CPU_OPT header.

It's entirely OP's decision at this point.

 

[mtcn77]

I read voltage control is easier on the fan motor. PWM signal has a pulse frequency which is not so fluid.
If you have free molexes lying around, you can fix your voltage fan to a lower fixed voltage rate, but PWM is smarter. It can restart your fan even if it failed to start. This can help when running the fan very slow.

 

[cvaldes]

I read voltage control is easier on the fan motor. PWM signal has a pulse frequency which is not so fluid.

That sounds mighty tenuous and unconvincing.

Looking at Noctua's 120mm fans the NF-A12x25 PWM, NF-A12x25 FLX (3-pin DC), and NF-A12x25 5V (3-pin 5V DC power) all have the same MTTF of >150,000 hours.

It appears that Noctua is unconvinced by your claim.

Is it something you "read on the Internet"? From a reputable source? One with peer-reviewed data backing up their claim? Or maybe it was a random Reddit hardware dilettante.

 

[mtcn77]

That sounds mighty tenuous and unconvincing.

Looking at Noctua's 120mm fans the NF-A12x25 PWM, NF-A12x25 FLX (3-pin DC), and NF-A12x25 5V (3-pin 5V DC power) all have the same MTTF of >150,000 hours.

It appears that Noctua is unconvinced by your claim.

Is it something you "read on the Internet"? From a reputable source? One with peer-reviewed data backing up their claim? Or maybe it was a random Reddit hardware dilettante.

This was before reddit when enthusiasts used to read review articles by real hardware editors.

 

[cvaldes]

Ah yes, way back in the Nineties when Shimpi was still writing for AnandTech and Pabst was writing for his namesake Tom's Hardware.

Good times, good times.

 

[mtcn77]

Ah yes, way back in the Nineties when Shimpi was still writing for AnandTech and Pabst was writing for his namesake Tom's Hardware.

Good times, good times.

Your name strikes a chord, but I'm not a fast fellow.

 

[cvaldes]

Trust me, I'm nobody, just another random anonymous schmuck on the Internet. This is just a random handle I occasionally use when signing up for Q&A forum accounts.

Anyhow, returning to the OP's original topic. Articles from the mid-Nineties about fans aren't particularly helpful in 2021. The overall product quality is much better today due to a combination of factors not limited to better design, better materials, tighter manufacturing tolerances, better QA, more reliable electronics, etc.

There was no Noctua NF-A12x25 PWM to shove in a beige ATX case in 1995.

 

[mtcn77]

Trust me, I'm nobody, just another random anonymous schmuck on the Internet. This is just a random handle I occasionally use when signing up for Q&A forum accounts.

Anyhow, returning to the OP's original topic. Articles from the mid-Nineties about fans aren't particularly helpful in 2021. The overall product quality is much better today due to a combination of factors not limited to better design, better materials, tighter manufacturing tolerances, better QA, more reliable electronics, etc.

There was no Noctua NF-A12x25 PWM to shove in a beige ATX case in 1995.

Dude.

Major Hardware 3D Fan Contest

I'm sure you have seen this. Major Hardware is petitioning people to design their own 3d printed fans. It is pretty exciting since one of the makers almost challenged Noctua 12x25, so there is plenty of reason to go and watch it.

www.techpowerup.com

 

[jesdals]

i've seen specific mobos that had zero voltage control on specific ports, it happens. Also have a fan controller that only outputs PWM, despite having a voltage in option.

On the Gigabyte x570 Master zero voltage control is an option

Btw Artic Cooler recommend PWM for their AIO arctic cooling liquid freezer ii series

 

[cvaldes]

Dude.

Major Hardware 3D Fan Contest

I'm sure you have seen this. Major Hardware is petitioning people to design their own 3d printed fans. It is pretty exciting since one of the makers almost challenged Noctua 12x25, so there is plenty of reason to go and watch it.

www.techpowerup.com

That is utter twaddle and completely irrelevant to the OP's situation.

Worse, the majority of those fan designs won't even fit in the standard 120mm x 25mm fan chassis, not to mention that these are all farcical and not a single one is a viable commercial product. Sure anyone can come up with a fan design the size of a grapefruit that moves a lot of air. So what? That doesn't help OP.

Let's stay on topic and save the Living in a Fan Dreamworld babble for its own thread. Maybe you're trying to pump up pageviews of your thread. Don't do it at the expense of this OP's predicament.

 

[mtcn77]

Worse, the majority of those fan designs won't even fit in the standard 120mm x 25mm fan chassis,

Look closer.