Gadgets are needed to comply with a protocol so which the interrupt-request (IRQ) lines is usually shared. The PCI bus features 4 interrupt traces, INTA# by INTD#, all of which are available to every system. As many as 8 PCI devices share the identical IRQ line (INTINA# by way of https://nathanlabsadvisory.com/certified-data-privacy-professional-cdpp/