 For example, a PCI extender board can be plugged into a PCI slot on a computer motherboard, and then a PCI card connected to the extender board to 'extend' the board into free space for access.This approach was common in the 1970s and 1980s particularly on S-100 bus systems.The concept can become unworkable when signal timing is affected by the length of the signal paths on the diagnostic board, as well as introducing Radio Frequency Interference (RFI) into the circuit under test because of a lack of adequate shielding.