Gadgets are needed to follow a protocol so which the interrupt-ask for (IRQ) traces is often shared. The PCI bus consists of 4 interrupt traces, INTA# by way of INTD#, all of which can be obtained to each gadget. Around 8 PCI equipment share the same IRQ line (INTINA# as https://nathanlabsadvisory.com/rbi-cyber-security-framework/