PCIe 3.0 x16 vs PCIe 2.0 x16 (x4 mode)?

Sep 3, 2018
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So 2 weeks ago I was building my 1st PC, and for some reason the GPU wouldn't send signals to the monitor if the tower stood upright... But if I put it on it's side it would work flawlessly. Weird...
Well I've just found out that the problem was the PCI Express slot itself. 2 pins inside it were bent, and if I use the other PCIe slot the tower can stand the way it is supposed to.



The specs of the build are: Gtx 1060 6gb, Ryzen 5 2600, 16gb 3200mhz RAM on a ASrock AB350M PRO4 motherboard.

How much of a performance hit should I expect using the PCIe 2.0 x16 (x4 mode) slot instead of the 3.0 x16?