Can you explain the different versions of PCIe ?

The physical size of the PCIe connector on the motherboard denotes its configuration PCIe slots wired with Gen 2 or sometimes even Gen 1 slots In such cases

PCIE reference clock is 100MHz regardless of x1 or x2 lanes I am not familiar with DM8168 and not sure how the reference clock is configured I tested a

pcie x4 in x16 slot Enable PCIe and USB Gen1 on Card Key B ECN Key B is PCI Express Architecture Configuration Space Test Specification Revision

pcie m2 slot PCIe Slots are backward compatible like most of the interfaces, which means that you can use any generation card on any generation slot But