CPU not running at Base Clock Speed

[thetechdummy]

Hello, I'm new to all this stuff.
I'm wondering whats keeping my CPU from running at a fixed speed 4.0Ghz, I watch some youtube videos like this (https://www.youtube.com/watch?v=-30Ab4l2apc) and it seems simple enough but my result isn't. I check task manager and the speed fluctuates at 3.78GHz to 3.95GHz.

CPU: Ryzen 5 2600
CPU Cooler: Noctua NH-U12S
Motherboard: MSI B450 Gaming Pro Carbon AC

 

[ElectrO_90]

it speeds itself up when it needs the power and slows its self down when it doesn't.
You don't need it to run max speed all the time.

 

[thetechdummy]

it speeds itself up when it needs the power and slows its self down when it doesn't.
You don't need it to run max speed all the time.

Well that make sense... but doesn't that negate the point of overclocking?
But I still want to know why some people's overclock stay at a fixed speed when they do it, mine don't.

 

[ElectrO_90]

It is normally to do with multiplier. This has to be set to an amount, say 40 which would be a constant of 4ghz.
It this is not set correctly then it will not run permentantly.

CPU-Z is good for monitoring speed multiplier.

 

[thetechdummy]

It is normally to do with multiplier. This has to be set to an amount, say 40 which would be a constant of 4ghz.
It this is not set correctly then it will not run permentantly.

CPU-Z is good for monitoring speed multiplier.

Thats what I did, just type in 40 in the bios and saved it, it said its at 4.0ghz but when I look at task manager the speed fluctuates below it