Products are necessary to stick to a protocol so that the interrupt-ask for (IRQ) lines may be shared. The PCI bus involves 4 interrupt lines, INTA# through INTD#, all of which are available to every product. As many as eight PCI devices share the same IRQ line (INTINA# through INTINH#) https://nathanlabsadvisory.com/total-block-chain-solutions/