Devices are needed to stick to a protocol so the interrupt-ask for (IRQ) lines can be shared. The PCI bus involves 4 interrupt traces, INTA# as a result of INTD#, all of which can be obtained to every gadget. Up to 8 PCI products share the same IRQ line (INTINA# https://nathanlabsadvisory.com/cybersecurity-fintechs/