Units are necessary to abide by a protocol so the interrupt-ask for (IRQ) strains may be shared. The PCI bus contains four interrupt lines, INTA# via INTD#, all of which can be found to each product. Nearly 8 PCI units share a similar IRQ line (INTINA# by INTINH#) in APIC-enabled https://nathanlabsadvisory.com/anti-money-laundering/