It's a power saving feature and is working normally. You can have your cpu run constantly at the boost clock by setting the windows power plan to high performance. You'll have to click "Show additional plans" .
Thanks for the answer and the video. I know about the energy saving settings and the maximum clock. My cores ran 1-2 months ago differently, as in the AMD video, they clocked differently and not all the same. 1 core was for example at 800MHZ and another then on 2ghz, they clocked differently and not all the same.
Edit: Also, all cores are now clocked at 5ghz in boost, before it was 1-2 cores if any that were briefly clocked up 5ghz in boost. When I start a game, all cores run normally at 4.7ghz. If I set the power plan to high performance, without an application in the background, then all cores clock to 5ghz, before all cores were at 4.7ghz.
I just found an old photo, there you can see what I mean, all cores clocked differently in desktop mode, Now they all clock the same. I would like to have it the way it used to be, like on my old photo here:
I made a video again, a game is running in the background, the power plan is on high performance and all cores clock normally at 4.7ghz. I quit the game and you can see how all cores are clocking at 5ghz which is not right. I change the power plan to balanced and all cores go to 800mhz which is normal but now when 1 core clocks up all cores clock up with it which was not before as you can see in the photo. Here is the video: https://www.youtube.com/watch?v=y0mufaupSJw
If I remember correctly, the 9900K should only reach 5ghz on 1 or 2 cores in boost and not on all at the same time?
My System: https://builds.gg/builds/my-little-hell-machine-28386