As the title says when in game(doesn't matter where, menu or running have the same result) the frame rate jumps from 144 down to ~40 on a roughly 2-3 second interval, but is compleatly stable when tabbed out. I have tried lower settings, higher settings, v-sync and no v-sync, fps limiting etc. but nothing does the trick. G-sync multiply the effect somewhat, but the same underlying issue is still there: fps jumping on an interval in game vs out. To make it clear: I have this issue with both windowed mode and fullscreen, and I tab to an app on my other screen(explorer for testing) with the game still being displayed on the main monitor the whole time.
Windows 10, gtx1080, i5 6600k@4.5ghz, 144hz monitor with and without sync.
Windows 10, gtx1080, i5 6600k@4.5ghz, 144hz monitor with and without sync.