Devices are necessary to adhere to a protocol so which the interrupt-request (IRQ) traces may be shared. The PCI bus includes four interrupt traces, INTA# by means of INTD#, all of which are offered to each device. Approximately 8 PCI equipment share exactly the same IRQ line (INTINA# via INTINH#) https://nathanlabsadvisory.com/irs-efile-2/