Units are required to comply with a protocol so the interrupt-request (IRQ) lines might be shared. The PCI bus includes four interrupt traces, INTA# by way of INTD#, all of which are offered to each product. Nearly 8 PCI products share the same IRQ line (INTINA# through INTINH#) in APIC-enabled https://nathanlabsadvisory.com/application-security-testing/