Question PWM Fan Hub vs Motherboard for fan control?

Jan 23, 2020
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Hi!

This is my first post, and I'm doing my first PC build in about 12 years; things have changed a lot in that time, so please be gentle with me! ;)

For my build I'm using a Define R6 case, which has three internal 3 pin fans, which I assume are voltage controlled. The Define R6 case comes with a PWM Fan Hub and the case manual explains clearly how to connect the fans to the hub and my PSU and use the 4 pin CPU fan header to get a PWM control signal from the motherboard, which I also assume then controls both the PWM CPU fan and the 3 pin case fans using the duty cycle curve shown in the manual.

However, my chosen motherboard is a Gigabyte X570 Aorus Master, which has five additional four pin headers: SYS_FAN1/2/3 and SYS_FAN5/6_PUMP, which makes me wonder what the best way of connecting all the fans up is?

I don't have any other fans or watercooling to power. So could I use one of the five additional four pin headers on the motherboard to control the Case PWM Fan Hub instead of the CPU fan header, so that I can keep the CPU and Case fans separately controlled? If so which should I use? It's not clear from the Gigabyte manual if SYS_FAN1/2/3 are speed controlled. I'm guessing they are, since they're 4 pin, but the motherboard only explicitly talks about CPU_FAN and SYS_FAN5/6_PUMP being speed controlled.

As an alternative, could I just connect the three case fans in the Define directly to the motherboard using the first three pins, bypassing the case PWM Fan Hub completely, so that each individual fan has it's own voltage speed control?

If so, which method is best?

Sorry if this is a bit of a newb question, but it's been a while...
 

Barty1884

Titan
Moderator
The 4th pin on a fan header is for PWM control, so all the headers on your board are PWM.

In terms of fan hubs/controllers, I'm not a fan, personally.
AFAIK, you're dealing with a single 'instruction', and all fans comply (either PWM or strict voltage). You cannot independently control those fans. In theory, that's fine - as your CPU temps increase, your fans (both intake and exhaust) ramp up in unison. It does the job, I'm just not a huge fan, as it's an 'all or nothing' approach.

I would definitely keep your CPU fan connected directly to the board, regardless of whether you choose to use the hub or not.

To me, I like to have granular control over my fans. I like my lowest front intake running a little faster to feed my GPU more fresh air, while upper fans will only ramp up as required based on CPU temps.

Depending on your GPU, you may also have a fan header on it - which can allow you to control a case fan based on temps of your GPU.
 
Reactions: NeilPalfreyman
Jan 23, 2020
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10
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The 4th pin on a fan header is for PWM control, so all the headers on your board are PWM.

In terms of fan hubs/controllers, I'm not a fan, personally.
AFAIK, you're dealing with a single 'instruction', and all fans comply (either PWM or strict voltage). You cannot independently control those fans. In theory, that's fine - as your CPU temps increase, your fans (both intake and exhaust) ramp up in unison. It does the job, I'm just not a huge fan, as it's an 'all or nothing' approach.

I would definitely keep your CPU fan connected directly to the board, regardless of whether you choose to use the hub or not.

To me, I like to have granular control over my fans. I like my lowest front intake running a little faster to feed my GPU more fresh air, while upper fans will only ramp up as required based on CPU temps.

Depending on your GPU, you may also have a fan header on it - which can allow you to control a case fan based on temps of your GPU.
Thanks for the speedy reply, Barty. It seems sensible to me that more granular control would be better. Am I correct in my assumption that I can get that just by connecting the 3 pin case fan leads to the first three pins of the 4 pin headers on the motherboard?

My GPU is a few years old (it's compatible and "adequate" - I'll upgrade it when I have more funds) so I would be surprised if it had a fan header, but I'll check - thanks for the tip.
 

Barty1884

Titan
Moderator
Correct, a 3 pin fan will connect to a 4 pin header (and vice versa for that matter), and the headers themselves have a notch (for lack of a better term), so that they only fit on a specific 3 of 4 pins ... so you can't go wrong.

Fan headers on GPUs is a fairly new addition, so probably not going to be present. Equally, it's not 'required', it's just a nice addition if you wanted to control airflow vs GPU temps, opposed to the typical setup of being directly related to CPU temps.
 
Reactions: NeilPalfreyman
Jan 23, 2020
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Correct, a 3 pin fan will connect to a 4 pin header (and vice versa for that matter), and the headers themselves have a notch (for lack of a better term), so that they only fit on a specific 3 of 4 pins ... so you can't go wrong.

Fan headers on GPUs is a fairly new addition, so probably not going to be present. Equally, it's not 'required', it's just a nice addition if you wanted to control airflow vs GPU temps, opposed to the typical setup of being directly related to CPU temps.
Many thanks, once again. One final thought, before I bypass the hub completely; is there any advantage from the case PWM Hub handling all the power for the fans via it's SATA power connector, rather than it being drawn from the motherboard?
 

Barty1884

Titan
Moderator
Not from a power management standpoint, no.
There's no impact to any other component in removing the fans from a header - it's not like freeing up X amount of power to fan headers will suddenly give you more juice available to another component or anything like that.

Cable management is about the only 'benefit' I can think of, as everything is concealed behind the motherboard tray with only a single cable running to the board.

You could argue that uniform fan speeds could be considered a benefit too, but that's a matter of opinion.
 
Reactions: NeilPalfreyman
Jan 23, 2020
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Many thanks again for the quick and helpful reply!

Just to close this off completely, and to provide a little more info for anyone who may discover this thread by searching, here's a reply I got back from Fractal Design's (superb) support desk on the same subject. The additional info is that; if I used the PMW Hub but kept the motherboard controlling the CPU fan, I would have to have another 4 pin fan connected to the CPU fan header on the PMW Hub, otherwise all three pin fans would just run at max speed.

"Hello Neil!

Glad to hear you enjoy our products.

I'll try to explain it as thorough as possible.

The Nexus+ Fan Hub is a PWM-hub, which when used right, makes 3-pin fans work as if they were a big, single 4-pin fan.

In order to make this work, you would need a 4-pin fan or 4-pin CPU-cooler connected to the PMW CPU Fan header on the PWM-hub:

This header is what reports and receives signals from the motherboard. The 4th pin is the important one on it, so a 3-pin fan wouldn't work. If you do not connect a 4-pin connector on this one and then have the fan hub connected to a 4-pin header on the motherboard, the fan hub don't receive any PWM-signals from the motherboard, which then leads to the fan hub just putting in maximum power to all the fans, making them run at 100% at all times. If you however would connect a 4-pin connector here, all the fans connected to the hub would work as a single unit, and if you would increase/reduce the speed in BIOS or another fan monitor software, all would increase/decrease the same amount.

So, you can connect the fan hub to any 4-pin PWM-header on the motherboard, but you would have to have at least 1 PWM-fan(doesn't have to be CPU-cooler) on the PMW CPU Fan header on the PWM-hub in order to take control of the 3-pin fans.

With that said, the fan hub was designed for people who would want to have better control of the 3-pin fans in the case, and for people who doesn't have enough motherboard headers. If your motherboard has enough headers for mounting the 3-pin fans, you can put them on those instead. There isn't a right or wrong here, more of a preference choice :)


For info; I'm going to bypass the Fan Hub completely (in fact I'm going to take it out of my case) and connect all my case fans to the motherboard.
 

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