Question Same fan curves, different behavior

Theberge43

Distinguished
Oct 13, 2007
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Hi,

So I've set CPU & Systems fans on the same curve (25C - 0% // 50C - 40% // 70C - 70% // 85C - 100% --- something like this) all based on CPU temperatures in the BIOS.
I'm confused that my System Fans don't run at all around 30C.

See screenshot:

https://prnt.sc/rbgp7x
 
Hi,

So I've set CPU & Systems fans on the same curve (25C - 0% // 50C - 40% // 70C - 70% // 85C - 100% --- something like this) all based on CPU temperatures in the BIOS.
I'm confused that my System Fans don't run at all around 30C.

See screenshot:

https://prnt.sc/rbgp7x
Temps when looking at them in BIOS are not same as under OS. Minimum temps at idle are greatly influenced by environment temperatures, typically higher by 10 - 15c than environment.
 

Theberge43

Distinguished
Oct 13, 2007
22
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18,510
0
Temps when looking at them in BIOS are not same as under OS. Minimum temps at idle are greatly influenced by environment temperatures, typically higher by 10 - 15c than environment.
Ok, but since the curves are set to the same temps, shouldn't they run at the same temps ? I understands that RPM can be different with different fan models, but at 30C they should all run at some degree.
 
Ok, but since the curves are set to the same temps, shouldn't they run at the same temps ? I understands that RPM can be different with different fan models, but at 30C they should all run at some degree.
Every type of fan has some starting voltage under which it will not even start. Are they voltage regulated or PWM ? BIOS should have a way to switch between those modes.
 

Paperdoc

Glorious
Ambassador
First of all, are you sure that all the fan headers are configured to use the CPU internal temperature sensor for their temp values? This is NOT the normal way to do things, and some mobos don't even give you that option. Most that do offer that option arrive pre-set by default to use the MOBO temperature sensor for the SYS_FAN headers, and that normally is the best choice.

Secondly, you should NOT set the minimum fan speed to 0% at the coldest. All fans have a minimum voltage or PWM setting to START them up, and a related minumum operating speed (set by voltage or PWM signal). If you feed the fan less than those minimum settings, the fan will stall and may not re-start. Normally the mobo will always start up all fans at 100% and then reduce to the required setting. The default mobo settings normally will not run the fans below 5 VDC in DC Mode, or about 30% in PWM Mode. But your custom "curve" tells it to reduce the fan signal to 0% PWM, so that certainly will stall the fan. THEN, as temperature increases, it will probably need to get up to a 40% to 50% signal at least just to re-START it. So, increase your minimum fan speed setting to 30% or more, and see if that solves your problem.
 

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