Units are required to observe a protocol so that the interrupt-request (IRQ) strains might be shared. The PCI bus consists of 4 interrupt lines, INTA# by INTD#, all of which can be found to every unit. Up to eight PCI equipment share the identical IRQ line (INTINA# through INTINH#) in https://nathanlabsadvisory.com/pci-pin-service/