[SOLVED] CPU Fan Spinning Pattern

[firstclick]

I just put together a system.

What I observed is that when the PSU is connected to power for the first time and you power the system, the CPU fan starts spinning, stops for a second and then continues spinning normally.

Then, if you power it off and then power it on any time afterwards, the CPU fan never stops spinning.

My assumption is that this is normal but would like to make sure.

 

[drea.drechsler]

Yes it's normal. That's because you could set up the system for 'full quiet' operation, where fans are normally not spinning until temperatures rise to a certain level. But then you may never know when a fan is failed so the BIOS will spin fans at high speed to test RPM at POST and alert you if one is failed.

The CPU fan is frequently the lone exception: in some systems it's set to always on, sometimes even at max voltage so max speed. That's because people often use AIO's with pumps that you might never know are working so take no chances and run them at max all the time. It's also a bit more careful since CPU's and their coolers retain heat at shutoff when fans stop, so for a restart it's good to ensure the fan's working right away.

What all that means is there is some logic about running the fans in BIOS that may be different at different points in operation: like a 'first power on' vs. a 'restart power on'.

 

[firstclick]

Phew, many thanks!