Gadgets are needed to comply with a protocol so that the interrupt-request (IRQ) strains could be shared. The PCI bus includes 4 interrupt lines, INTA# by INTD#, all of which are available to every device. Up to eight PCI units share the identical IRQ line (INTINA# by INTINH#) in APIC-enabled https://nathanlabsadvisory.com/spear-phising/