Can I put a PCI-E x16 gpu in a PCI-E x16 slot?

Using a PCIe x1 card in a PCIe x16 slot pcle x16 slot It's a slot of x16 size but electrically x4 This pcle x1 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

pcle slot MOBO and GPU compatibility warning One additional PCIe x16 slot is needed