Question Graphics Card Runs Slower at PCIe x16?

Sep 23, 2021
I built a new system (but am using my old graphics card a Nvidia 1060 GTX).

On my motherboard, if you put a card in the second PCIe x16 slot, then the first slot runs at x8. When the graphics card was running at x8, I checked in HWInfo and it said in the "system summary" that the Graphics card bus was "PCIe v3.0 x16 (8.0 GT/s) @ x8 (8.0 GT/s)" With the information after the @ sign, being the active bus settings.

Now if I remove the card from the second PCIe x16 slot, and the graphics card now runs at x16, it now says under HWInfo in "system summary" that the graphic's card bus is at "PCIe v3.0 x16 (8.0 GT/s) @ x16 (2.5 GT/s)". Again the active bus settings are after the @ sign.

Why is it running at 2.5 GT/s which is slower in x16, then the 8.0 GT/s when it is running at x8?