The Network Instruments PCI DEC Chipset 21140 is a network interface card (NIC) that uses the DEC 21140 chipset, which was a popular Ethernet controller in the late 1990s and early 2000s. This chipset provides Ethernet connectivity over a PCI bus and supports speeds of up to 100 Mbps (Fast Ethernet). The driver for the DEC 21140 chipset allows the operating system (such as Windows) to properly communicate with the network card, enabling the computer to send and receive data over a local area network (LAN).