Graphics card clocks down after some time in the game?

My graphics card (AMD Radeon R7 m370 (laptop)) clocks at game start with full 875 MHz. But after a short time in the game, the clock rate goes down to 300 MHz and no longer high. Is that due to any wrong attitude or is it due to other reasons?

P.S. Driver is up to date; CPU: Intel Core i7 -6500U 2.5 GHz; SSD; 8 GB RAM

Small attachment: The new hard drive is from another computer, where it works.

The temperature will be the problem. If the chip is too hot is down clocked.

Does that affect your game? If no performance is requested from the game, then many graphics cards also go down again.

Can you turn it off or should not you change anything there?

Probably temperature problems.

You do not want to switch off, if you want to use the hardware in the future. The solution would be to get better CPU and GPU cooling.

You can also use tools like HWMonitor to read temperatures during play to see if they are really too high.

Yes, e.g. I bought a new game, which initially ran at 60 FPS and the next day when I started it I had only 20 FPS

OK thanks

Do you have to check with MSI Afterburner?

… With such an old notebook, it will probably have come to dusting in the cooling… The cooling system times clean… Do you usually so every 1/2 years.

Are about 60 ° too much?

No. This is in the normal range.