Units Are necessary to observe a protocol so which the interrupt-request (IRQ) traces is usually shared. The PCI bus consists of four interrupt traces, INTA# through INTD#, all of which are available to each gadget. As many as 8 PCI gadgets share precisely the same IRQ line (INTINA# through INTINH#) https://nathanlabsadvisory.com/financial-cyber-security-consulting/