Devices are required to abide by a protocol so that the interrupt-request (IRQ) strains can be shared. The PCI bus involves 4 interrupt strains, INTA# by means of INTD#, all of which are offered to every unit. As many as 8 PCI gadgets share a similar IRQ line (INTINA# via https://nathanlabsadvisory.com/red-team-exercise/