Circuit board for connecting to a computer system to add functionality Example of a PCI digital I/O expansion card using a large square chip from PLX Technology to handle the PCI bus interface PCI expansion slot Altair 8800b from March 1976 with an 18-slot S-100 backplane which housed both the Intel 8080 mainboard and many expansion boards Rack of IBM Standard Modular System expansion cards in an IBM 1401 computer using a 16-pin gold plated edge connector first introduced in 1959 Configuration DIP switches in a 16-pin through-hole package as often found in ISA expansion cards from the 1980s Thunderbolt 3 connector introduced by Intel in December 2015 multiplexes up to 4-lanes of PCIe 3.0 and 8-lanes of DisplayPort 1.2 and can support an external docking station housing one or more expansion cards with enough bandwidth to drive a mid-range GPU
