Devices are necessary to stick to a protocol so the interrupt-request (IRQ) traces can be shared. The PCI bus includes four interrupt traces, INTA# via INTD#, all of which can be obtained to every product. Nearly 8 PCI equipment share the identical IRQ line (INTINA# via INTINH#) in APIC-enabled x86 https://nathanlabsadvisory.com/financial-cyber-security-consulting/