Devices Are necessary to observe a protocol so the interrupt-request (IRQ) strains could be shared. The PCI bus incorporates 4 interrupt strains, INTA# by INTD#, all of which are offered to each gadget. As much as eight PCI gadgets share the same IRQ line (INTINA# via INTINH#) in APIC-enabled x86 https://nathanlabsadvisory.com/ensuring-secure-payment-processing-with-pci-dss-compliance-certification-in-the-usa/