Can I put a PCIE X8 GPU in a PCie X16 slot?

pcie 8x slot   Dan pcie 8x slot

PCIe slot

as you have a Non G Processor that top slot should be running at full x16 speed the Top is coming Directly off the Last 4 PCI-E lanes There are two components to a PCIe slot: mechanical and electrical For instance, you can have a slot that is x16 mechanical

double blessings slot machine For instance, you can place a PCIe x8 card into a PCIe x16 slot when the PCIe x8 slot has been occupied, but that card will always run in PCIe even though the slot may be wired as x8 electrically There is also the caveat that if you have a weaker CPU you may be gimped