These are PCIe x1, x2, x4, x8, and x16 ... This (traditionally) now means network cards and wireless modules, such as Wi-Fi ...

The common hardware interface in PCs, Macs and other computers for connecting peripheral devices such as storage drives and graphics cards. PCI Express ... serial lanes (x1-x32) that transfer ...

This showed that the Raspberry Pi would happily talk with a VL805-based USB 3.0 PCIe expansion card, as well as a Realtek RTL8111-based Ethernet card ... have both PCIe x1 and USB on a Raspberry ...

PCIe x4 and x8 cards can draw up to 25W from the motherboard's slot, while x1 cards are limited to 10W unless configured as a 'full-height' or 'high-power card' to pull the aforementioned 25W.