Question Loud CPU w/ C-States enabled

May 29, 2019
Hi all,

I recently put together a new build. After getting everything put together, and moving past the BIOS, I started noticing a strange scratching/clicking sound coming from inside my case. If I hadn't bought a SSD, I would have just assumed that it was the HDD doing its thing. It's not incredibly loud, but definitely noticeable above my case fans.

I tried putting up with it for about a week, but then the persistent sound of an old harddrive going through the motions annoyed me so much that I wanted to punch a baby seal in the face. At first, I thought it was the SSD, as some articles/videos had talked about SSDs having a slight "singing" to them. And at first, this satisfied me, but I was noticing that it was happening regardless of the load on the SSD, and moresoe when idling. So, after some digging, I ended up on some random Dell Customer Service page that mentioning something about disabling the C-states, as the CPU's main power circuit can make sounds. So, in order to save so many baby seals, I gave it a shot. Sure enough, it worked. With C-states disabled, the sound went away.

So, the questions are:

Is this in any way normal?
Is it harmful to disabled c-states?
Does anyone know any good online guides to the different C-states (as the BIOS has many options if it is enabled, and I was going to Trial and Error my way through it to see if I could isolate the main offender)?

Preemptive thanks.

Asus Prime Z390-A
Intel i5-9600K Coffee Lake
G.Skill Ripjaws V Series 32GB DDR4 3200
Samsung 970 Evo Plus SSD 1TB
EVGA SuperNova 650 G5 PSU
Corsair Hydro Series H100i PRO RGB AIO
Cooler Master MasterCase H500
Windows 10 Pro
C-states have nothing to do with scratching/clicking sounds. They are just different power modes for your CPU... for example when you aren't doing anything the processor enters an idle state in which voltage and clock speed are reduced.

Now for your problem... open your case and try to locate from where the sound comes. Most likely it's one of your fans hitting something(without a HDD they're the only moving parts in your PC, hence they're probably the culprit).
Thanks for the replies. If it were a fan problem, why would disabling the C-states stop it from happening?
Apparently you're right... I have built PCs for a long time and I've never encountered it on a motherboard. It's something new for me too... you learn something new everyday huh?

It's some sort of coil whine... more common on GPUs, as the power draw changes electrical frequency changes making the coils vibrate at a a different pitch(making the noise more or less annoying).

The same process is happening accross the power delivery to your CPU... which is on your motherboard. Disabling C states won't allow your CPU to go into that low voltage/clock speed mode(will slightly increase temps), that prevents you from hearing that "annoying" sound because that particular coil vibration pitch is produced at a lower voltage(certain idle state or C state).

It's something pretty rare as you can see, but some motherboards behave like that.

Good news are that there's nothing to worry about, it's just that in particular conditions coils vibrate at an annoying frequency perceived by the human ear... otherwise the motherboard is operating as it should.

EDIT: Made some adjustments in my explanations
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