Gtx 1070ti problem

Jul 24, 2018
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Hello, a few days ago i got a gtx 1070ti, it wasn't brand new but it wasn't used a lot. I've had an R9 380 4gb version. Every game that i play with and 1070ti runs at 60fps no problem, but every 10-30 seconds it drops down to 5-30 fps. I've tested a few games and it happeneds everywhere.
Non of my components are overheating, i've uninstalled the drivers three or four times with ddu in safe mode, and it doesn't help. My windows 10 (64-bit) is up to date.The ram is only used 60-70% at a time, so it's not the problem Underclocking or Overclocking dosen't help either. I'm all out of ideas, so any help would be appriciated.

GPU:GTX 1070ti
CPU:i7-7700k
RAM:8gb
OS:Windows 10 (64-bit)