Question Is it a good idea to connect ALL fans(case+cpu) to CPU_FAN ?

knowledge2121

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I have a Gigabyte z170x gaming 3.

When i go to the BIOS's smart fan 5, the graph for case fans are pwm vs temp...the manual says that case fans are voltage controlled and CPU_FAN is pwm controlled...I am assuming the case fans are voltage controlled ? Does smart fan 5 get updated as well when updating the bios ?

I have several Arctic p12 pwm fans for case fans and 2x cpu fans(dark rock pro 4)..I want to connect all of these fans to a pwm fan hub and then connect the fan hub to CPU_FAN....Is there a problem with this setup ?

I know that with this setup all fans' speeds are governed by cpu temperature...but is there a problem with that ?
 

Cem Goker

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Does the PWM fan hub come with its own power cord that is directly connected to the PSU? If the PWM hub is also powered by the motherboard fan header I highly suggest that you do not connect all your fans to the PWM hub to a single fan header. At most, one PWM fan header will be able to handle 3-4 fans at most (ideal to keep it below 1 amps of power per header). A typical 120mm case fan has 0.20~0.25 amps of power requirements so you can go from there in terms of connections to the motherboard fan headers.
 

knowledge2121

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The hub i am using is powered by SATA(4.5A MAX).. each port on the hub supports max 1A..

The 2x cpu fans are both rated 0.08A each..
And the rest are rated 0.16A each..I have calculated the total current my fans require and there is enough power...

Are there any downsides to let the cpu temp govern ALL fans' speed ?
 
I would not do it. Power-wise it will work, because of that hub, but should the cpu run cool, and therefore lower ALL fan speeds, then other components could be running warmer unneccessarily. You want to maintain decent case airflow regardless of cpu temp
 
I have several Arctic p12 pwm fans for case fans and 2x cpu fans(dark rock pro 4)..
I want to connect all of these fans to a pwm fan hub and then connect the fan hub to CPU_FAN....Is there a problem with this setup ?
How much is "several"?

All fan headers on Gigabyte z170x gaming 3 are 4pin. So all of them are PWM regulated.
In BIOS you may have option to change fan regulation type.

Connect cpu fans to CPU_FAN and CPU_OPT headers.
Connect system fans to SYS_FAN1, SYS_FAN2, SYS_FAN3 headers.
 

Paperdoc

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You are correct - the SYS_FAN headers on that mobo are spec'd in the manual to be ONLY Voltage Controlled. The fact that they have 4 pins does NOT prove they can do PWM.

You would be best to control all the case fans by one of the SYS fan headers because they use a different temperature sensor from the one inside the CPU chip. You have two choices for this.

1. Any PWM fan CAN have its speed controlled by the older Voltage Control system, although this is not ideal technically. IF you want to do this with "several' PWM 4-pin case fans you can do that using a simple SPLITTER, not a HUB, as long as you are sure the total max current for the group is not over 1.0 A. A SPLITTER has one input "arm" that plugs into a mobo SYS_FAN header and several outputs that provide power to fans. It has NO other connections so ALL fan power comes from the host header. A HUB can be distinguished because it also has an "arm" that must plug into a SATA power output from the PSU to get power to all its fans; it does NOT draw power from the host header.

2. Use a fan HUB that gets power from the PSU. As you have anticipat4ed, this is a problem for you because all Hubs REQUIRE a PWM signal from the mobo host header. BUT there is ONE that is different and CAN work for you - the Phanteks Universal Fan Hub. It has both 3-pin and 4-pin output ports for using different fan types. But most importantly it CAN accept input from a host header with EITHER Voltage Control or PWM Mode signals. It recognizes whatever input signal it gets and "translates" that into both PWM Mode (for it 4-pin outputs) and Voltage Control Mode (for its 3-pin outputs) signals. So it truly CAN work with either input signal form and both types of fans. This one WILL let you connect your PWM fans to your SYS_FAN header and control them optimally.
 

Paperdoc

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P. 14 where details are shown for the fan headers. Note that CPU_FAN header has "+12v" (fixed) on Pin 2 and "Speed Control" on Pin 4. That indicates it is putting out the PWM signal set. The three SYS_FAN headers all have Pin 2 as "Speed Control" and Pin 4 as "VCC". They control speed by varying the VOLTAGE on Pin 2 and have a fixed DC signal on Pin 4 that is NOT the PWM signal to help 4-pin fans adapt to that Voltage Control Mode signal set.
 

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