Units Are necessary to adhere to a protocol so the interrupt-request (IRQ) lines is usually shared. The PCI bus features four interrupt traces, INTA# through INTD#, all of which can be found to each device. As many as 8 PCI units share a similar IRQ line (INTINA# as a result https://nathanlabsadvisory.com/key-components-of-a-successful-incident-response-strategy/