Equipment are necessary to adhere to a protocol so the interrupt-ask for (IRQ) lines might be shared. The PCI bus contains 4 interrupt lines, INTA# by INTD#, all of which are available to each device. As many as 8 PCI units share the identical IRQ line (INTINA# by INTINH#) in https://nathanlabsadvisory.com/spear-phising/