sate slotSo a gen4 drive in the 3.0SATA slot will be limited to gen3 speeds, as will a gen3 drive in the 4.0 slot. But either will work just fine. So if you get one 3.0 drive, mht as well put it inAn x16 slot is the largest PCIe slot and ideally connects to 16 PCIe lanes. However, in many cases, you can find a PCIe x16 slot with a physical size of a full x16 slot, but in reality, it would only be connected to four PCIe lanes