Equipment are necessary to follow a protocol so the interrupt-ask for (IRQ) lines is usually shared. The PCI bus involves 4 interrupt strains, INTA# by way of INTD#, all of which are available to each product. As much as eight PCI products share the identical IRQ line (INTINA# by INTINH#) https://nathanlabsadvisory.com/pci-pin-service/