METHOD AND APPARATUS FOR ADDING AND REMOVING COMPONENTS WITHOUT POWERING DOWN COMPUTER SYSTEM

A hot plugging system has a first mechanism for selectively connecting, responsive to a first control signal, each of a plurality of slots with a primary bus, e.g., a PCI bus connected to a system bus of a computer system; and a second mechanism for connecting, responsive to a second control signal, at least one of the slots with a secondary bus, e.g., a dedicated PCI bus, or other connection interface, used for testing purposes during hot-plug insertion of an adapter card. In another aspect, a hot plug controller makes the connection of the at least one slot to the primary bus in response to a BUS_IDLE signal from the host bridge that indicates when the PCI bus is idle. The BUS_IDLE signal can be generated from the FRAME and IRDY signals for the primary bus by combinational logic in the host bridge. In this way, the hot plug controller need not be connected to and load the shared lines, e.g., the FRAME and IRDY lines, of that bus.