Devices are required to abide by a protocol so which the interrupt-ask for (IRQ) lines is usually shared. The PCI bus incorporates four interrupt lines, INTA# via INTD#, all of which are available to every machine. Nearly 8 PCI gadgets share the identical IRQ line (INTINA# by means of INTINH#) https://nathanlabsadvisory.com/cybersecurity-technical-writing/