pci slotPCIe slots come in a variety of physically different sizes referred to by the maximum lane count they support, ie. x1, x2, x4, x8, x16, and x32. A PCIe card will fit into a slot of its size or bger,Learn about PCI, a standard information transport for extension cards in computers from 1993 to 2007. Find out the types, function, advantages and disadvantages of PCI slots and how they differ from PCI Express.