Units are needed to comply with a protocol so which the interrupt-ask for (IRQ) traces might be shared. The PCI bus incorporates 4 interrupt strains, INTA# by INTD#, all of which are available to every gadget. Nearly eight PCI gadgets share the exact same IRQ line (INTINA# via INTINH#) in https://nathanlabsadvisory.com/copyright-currency-security-standard/