Riser with Three PCIe Gen3 FH slots One x16 and 2 x8

Yes, a x1 card should work in a x16 slot It's good that you've got it to work in a x1 slot What else have you tried it in besides the x16 slot

So, there is no singular PCI Express slot There are actually four sizes : PCI Express x1, PCI Express x4, PCI Express x8, and PCI Express x16

x16 slot On PCIe X1, X4 and X16 slots, the first 18 pins are all wired the same, so as long as the PCI-Express card fits in the PCI-Express slot, it

piggy bank bills slot A x8 card will work in an x1 slot, but will be limited to x1 speeds A x8 card will also work fine in a x4 slot It will be limited to x4 speeds