[SOLVED] The Fan Hub Mystery!

kulike

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Hi everyone,

I found myself in a bit of a confusing situation and was wandering you you could help me out in identifying the problem.

I have recently brought a new budget PC case which came with a Fan hub. I never had a hub before so I figured why not use it.

I have an Asus Sabertooth 990fx r2.0 (old i know) which has 4pin system fans. https://www.asus.com/uk/Motherboards/SABERTOOTH_990FX_R20/

The hub itself only supports 5 3-pin fans but uses a 4-pin cable to connect to the motherboard, which makes me believe that it can control the speed of the 3pin fans. http://www.gamemax.uk/index.php/products/cases/black-hole-argb-mid-tower/

The problem is that when I connect the hub to the motherboard the fans spin and stop every few seconds as if not enough voltage is going into them. I figured maybe it's the motherboard but all the other system fan connectors behave the same way. (funny enough, when I connect the hub to only 3 of the 4 pins on the motherboard, the fans work but at full speed).

This is when I tried to connect the hub to a cpu slot and it WORKS! with all 3-pin fans speed controlled ie spinning faster when cpu gets hotter.

This made me believe that maybe the system fan connectors are faulty, but out of curiosity, I connected some 4-pin fans to to the motherboard (not cpu plug) and they all work with their speed controlled as well.

So the hub works as it should when plugged to a CPU_fan, but not when plugged into the Sys_fan, unless only connexted to 3 out of 4 pins but then only works at full speed, whereas some spare 4-pin fans work normally when connected to the Sys_fan.

So technically everything works but not where I want them to be.

Anyone have ideas what the issue is ??? Thanks!

Appologies for the over descriptive text, but this situation scrambled my brain.
 
your motherboard fan ports are controlled by the BIOS. each port can be set at individual speed profiles based on the temperature of the CPU and other temp sensors placed around the motherboard.

the CPU_FAN port is almost always going to be defaulted to run faster than most, based on CPU temps.

SYS_FAN(or similar named) ports will usually be set based on other location's temps.
the fan speed curve profiles being used for these ports are probably not set to start running at a high enough % at low enough temps for them to kick the fan hub into working correctly.
changing these fan speed curve profiles to start running at higher % while at lower temps should allow the fan hub to also function correctly through these ports.
 
Reactions: kulike
your motherboard fan ports are controlled by the BIOS. each port can be set at individual speed profiles based on the temperature of the CPU and other temp sensors placed around the motherboard.

the CPU_FAN port is almost always going to be defaulted to run faster than most, based on CPU temps.

SYS_FAN(or similar named) ports will usually be set based on other location's temps.
the fan speed curve profiles being used for these ports are probably not set to start running at a high enough % at low enough temps for them to kick the fan hub into working correctly.
changing these fan speed curve profiles to start running at higher % while at lower temps should allow the fan hub to also function correctly through these ports.
 
Reactions: kulike

kulike

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Apr 14, 2013
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I did notice in tee manual that the system fans profile is

GND
CHA FAN PWR
CHA FAN IN
+5V

Whereas the cpu one is:

GND
CHA FAN PWR
CHA FAN IN
CPU FAN PWM

could this be the cause? I tried to play around wit the settings on bios but I'm not getting anywhere!
 
look in your ASUS user manual and it will usually show how to control your own fans.

whatever ASUS Windows motherboard control software was released with the board should have all of these settings available to customize and save. download the latest version available from the ASUS product information page for your motherboard.

the BIOS settings relating to fans should be something like:
Profile - PWM / DC
and an option to create custom speed curve profiles for each port.
 

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