Network Interface Cards or network adapters are commonly connected to Peripheral Component Interconnect Express x1 and PCI expansion slots in a desktop computer. These slots are prevalent so expansion won't be a problem if you have free slots. NICs include Ethernet adapters and Wi-Fi adapters. Laptops can use Express Card and PC Cards to add NICs. Both desktops and laptops can forgo using an internal card in favor of a USB NIC adapter.
NICs add network communication functionality to a computer. Computers need NICs to communicate over networks. Ethernet adapters use a wired connection to connect to a router or modem. Wi-Fi adapters communicate with wireless routers via radio. Most desktop computers have built-in Ethernet adapters, while laptops usually feature built-in Ethernet and Wi-Fi adapters.
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Most NIC devices that use the PCI Express expansion slot type use the slowest and smallest type: PCI Express x1. PCI Express devices add additional channel connectors to use more bandwidth when communicating with the computer. A PCI Express x1 card can fit in larger slots including PCI Express x4 slots and PCI Express x16 slots; however, the cards won't use the additional slot bandwidth. The single channel connector has sufficient bandwidth to handle the NIC's maximum data transmission rates.
NICs also use the older PCI standard. PCI Express superseded PCI, but the PCI standard has sufficient bandwidth to handle the maximum data speeds for NICs that use up to gigabit connections. PCI compatible NICs can be used in cases when the computer doesn't have open PCI Express slots. The PCI standard is found in almost any desktop computer made since the mid 1990s and still appears in modern computers for legacy support. PCI slots are physically longer than PCI Express slots.
ExpressCard and PC Card
Laptops usually have built-in Ethernet and Wi-Fi but can add NICs through the PC Card and ExpressCard connection standards. PC Cards and ExpressCards slide into a slot on the side of compatible laptops: They function similarly to expansion board slots. PC Cards have similar performance to PCI devices and ExpressCards perform about two and a half times as fast as PCI devices.
NIC devices can also use USB to connect to computers. The external USB standard enables you to add a NIC to a computer without having to open it. Additionally, USB works with laptops that don't feature ExpressCard or PC card support. USB devices perform faster than PCI devices, but slower than PCI Express devices. With the exception of first generation USB devices, the standard is fast enough to handle the maximum speed of a gigabit NIC device.