Equipment are needed to observe a protocol so the interrupt-request (IRQ) strains is usually shared. The PCI bus includes 4 interrupt lines, INTA# via INTD#, all of which can be obtained to every device. Around eight PCI devices share the exact same IRQ line (INTINA# through INTINH#) in APIC-enabled x86 https://nathanlabsadvisory.com/ciso-services-virtual-ciso/