Equipment Are required to abide by a protocol so that the interrupt-request (IRQ) lines could be shared. The PCI bus contains four interrupt traces, INTA# through INTD#, all of which can be obtained to every gadget. As many as eight PCI gadgets share the same IRQ line (INTINA# by INTINH#) https://nathanlabsadvisory.com/navigating-cybersecurity-and-risk-management/