Products are required to observe a protocol so that the interrupt-request (IRQ) lines is often shared. The PCI bus includes four interrupt lines, INTA# through INTD#, all of which can be obtained to every device. Approximately 8 PCI equipment share the identical IRQ line (INTINA# by INTINH#) in APIC-enabled x86 https://nathanlabsadvisory.com/industries/