I noticed such an FPS drop today and it seems that it is a consequence of GTX 1050 running PCIe x16 1.1
As I got it, there several modes for GTX 1050 being engaged. During demanding tasks, like games, it uses all 16 PCIe 3.0 lines and maintains 8,0 GT/s transfer speed. In a mid-range tasks it uses 8 lines of PCIe 3.0 and in light mode it runs with 16 lines of PCIe 1.1 with 2,5 GT/s bandwith. I've noticed that sometimes switch btw this mode fails, and in-game it works PCIe x16 1.1 2,5 GT/s, but when you switch to desktop it goes PCIe x16 3.0 8,0 GT/s.
But what causes this stagger - don't know exactly. I think that this is Nvidia Optimus malfunction, because it is capable of switching graphic adapter modes even when you alt+TAB to desktop from games. Also, because no thermal or power throttling occurs, both CPU and GPU: CPU runs 2,398 Mhz as it must and GTX 1050 - 1,709 Mhz core and 3504 Mhz memory.
P.S.: everything has it positives - ice-cold 65°C CPU and 60°C GPU is something I see in my dreams ( ͡° ͜ʖ ͡°)
Upd: I was mistaken. It still runs 8,0 GT/s. and switches to 2,5 GT/s only for a moment, when I alt-tabed.
