Devices are necessary to follow a protocol so that the interrupt-request (IRQ) strains is often shared. The PCI bus involves four interrupt lines, INTA# by way of INTD#, all of which are available to each device. As much as eight PCI units share the identical IRQ line (INTINA# via INTINH#) https://nathanlabsadvisory.com/difc-data-protection-compliance/