What is the difference between CPU_FAN and SYS_FAN?

[Imacflier]

Morning, All,

On my Gigabyte ITX Motherboard (GA=Z97N-WIFI) there are two four pin ports. One is labled CPU_Fan, the other SYS_Fan. One would think there is some difference in their operation.

Does anyone know the difference between them? I am trying to discover the best hook up logic for a water cooling pump, the water cooling fan, and the system fans.

I am SURE one of you bright guys knows for sure.

Please share your wisdom with me?

Larry

 

[drea.drechsler]

On some motherboards the CPU_Fan must have a fan installed and reporting RPM, i.e., be operational, in order to POST and start the boot process (there may be a BIOS option to disable that test if the CPU is using passive cooling). Also on some motherboards the CPU_Fan is the only fan header that can be controlled and/or is keyed only to the CPU temperature.

Sys_Fan, in contrast, may not be speed controllable and/or may be keyed to some other temperature indicator, e.g., motherboard or chipset temp.

Not sure what the case is with your particular motherboard.

For most people it's best to operate the pump at 100% all the time so you can simply connect it to a SATA power cable and then connect the radiator fans to the CPU_Fan header to control them and keep it quiet until needed. Some motherboards have a CPU_Pump header that operates at 100% but reports RPM and is monitored so if it fails the system will go into alarms or shut down.

 

[Imacflier]

On some motherboards the CPU_Fan must have a fan installed and reporting RPM, i.e., be operational, in order to POST and start the boot process (there may be a BIOS option to disable that test if the CPU is using passive cooling). Also on some motherboards the CPU_Fan is the only fan header that can be controlled and/or is keyed only to the CPU temperature.

Sys_Fan, in contrast, may not be speed controllable and/or may be keyed to some other temperature indicator, e.g., motherboard or chipset temp.

Not sure what the case is with your particular motherboard.

For most people it's best to operate the pump at 100% all the time so you can simply connect it to a SATA power cable and then connect the radiator fans to the CPU_Fan header to control them and keep it quiet until needed. Some motherboards have a CPU_Pump header that operates at 100% but reports RPM and is monitored so if it fails the system will go into alarms or shut down.

Thank you. By actually READING the user's manual, it turns out that the two ports on this board are virtually identical, but with separate fan curves available in BIOS.

By chance you even answered my NEXT question: 'should I run the pump at 100% ALL the time?'

Again, many thanks!