CPU Fan or Motherboard?

My CPU fan stutters at start up, runs normal speed, and then slows down upon entering desktop. I have no power saving settings in my bios or anything that would cause this and my CPU fan has never done this before now. Could this be a faulty motherboard or faulty CPU fan? No, it is not just too dusty.

System is an FX-6300 with stock fan on a Gigabyte 970-DS3P

I am not sure if AMD cool 'n Quiet Tech has anything to do with it, but you did say you have no power saving settings on in your mobo. But did you check around to see if the board has the "Smart Fan" function? I know it's on a lot of prebuilt systems, and could be on consumer boards. Check for that, if it is on, it will slow down to its lowest speed depending on CPU temp.

Yup this is a default feature on just about if not every AMD board. Head into BOIS/UEFI and turn it off. Should fix it, if not come back and post continuing issues as they come.

Seems to have done the trick. The setting must have been changed when I updated the BIOS. Thanks