Devices are required to stick to a protocol so which the interrupt-request (IRQ) strains is often shared. The PCI bus includes four interrupt lines, INTA# by INTD#, all of which can be obtained to each gadget. Around 8 PCI products share a similar IRQ line (INTINA# by way of INTINH#) https://nathanlabsadvisory.com/infrastructure-security-testing/