pci slotPCIe Slot Structure. All PCIe slots are divided into two parts by a small protrusion in the middle separating them. This is why PCIe expansion cards, such as graphics cards,Learn about the different types of slots on the motherboard, such as PCI, PCIe, PCI-X, AGP, ISA, EISA, VESA, RAM, AMR and CNR. Find out their purposes, features,