The 100Fx DC21143 Fast Ethernet PCI Bus Adapter is a network interface card (NIC) based on the Digital Equipment Corporation (DEC) 21143 chipset, which is commonly used to enable Fast Ethernet (100 Mbps) network connections on computers. This adapter was widely used in older PCs and workstations, especially in the late 1990s and early 2000s, and was a popular option for connecting to local area networks (LANs).

The Windows driver for this adapter allows the operating system to communicate with the hardware, enabling network functionality. Without the driver, the operating system won't be able to recognize or properly use the network card.