Each attention button is tied to a presence signal, which is also used to detect the presence of a PCI adapter card within a slot. By comparing HPPC register states, pending due to a system control interrupt ("SCI"), with stored HPPC register states prior to the SCI, the HPPC is able to distinguish between an attention button press and a PCI card insertion or removal and therefore may respond appropriately to the SCI. According to the method, SCIs generated in a computer system by attention buttons are diagnosed and serviced by storing the contents of the HPPC registers. The contents of the registers identify the state of the presence and manually-operated retention latch ("MRL") signals prior to the occurrence of a SCI and upon receiving a SCI corresponding to a state change for either signal, identify the hot plug controller and the slot where the interrupt occurred.