Equipment are necessary to adhere to a protocol so which the interrupt-ask for (IRQ) lines is usually shared. The PCI bus features four interrupt traces, INTA# through INTD#, all of which can be found to every system. Up to eight PCI products share the identical IRQ line (INTINA# via INTINH#) https://nathanlabsadvisory.com/iso-27001-information-security/