Abstract: An apparatus and method for determining the types of expansion cards connected to the expansion slot connectors of a computer system. Detect signals are provided to decode logic for determining the types of expansion cards connected to the computer system. If the expansion cards are compatible the decode logic produces an output power supply signal that indicates what the voltage level should be for the power supply to the cards. If the cards are incompatible, the decode logic may not provide power to any of the cards or only provide power to some of the cards that are compatible. For computers that allow expansion cards to connect to the computer while the computer is powered on, hot-plug logic cooperates with the decode logic to establish power and communication with newly connected interface cards. The connectors in the computer do not include keys and thus interface cards without keys, as well as cards with different types of key arrangements can be connected to and communicate with the computer.