The Supermicro X9DRL-EF comes with two PCI Express 3.0 x8 slots, one PCI Express 2.0 x8 slot (working at x4), and one PCI Express 2.0 x1 slot.
Since servers don’t require high-end video cards, PCI Express x16 slots are not provided.
Each CPU controls one of the PCI Express 3.0 x8 slots. The third PCI Express x8 slot uses the 2.0 specification, works at x4 speed, and is controlled by the chipset. The PCI Express 2.0 x1 slot is also controlled by the chipset.