These modems would often slot into a Mini PCI-e slot in the netbook motherboard. [delokaver] figured out how to use these 3G cards over USB instead. It’s actually a fairly straightforward hack.

A PCIe expansion card uses your extra PCIe sockets to add new capabilities to your PC, like faster Ethernet, more USB sockets, or Wi-Fi and Bluetooth capabilities, which can be genuinely useful ...

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, but not a number of other PCIe cards.

All of the adapters below are available as external USB modules as well as PCI or PCI Express (PCIe) cards that plug into an empty slot on the motherboard. See PCI and PCI Express. Cellular ...

Typically available as an external USB module, for desktop computers, the modem may also be available on a PCI or PCI Express (PCIe) card that plugs into an empty slot on the motherboard.