Products are needed to adhere to a protocol so the interrupt-request (IRQ) lines is often shared. The PCI bus consists of four interrupt traces, INTA# by means of INTD#, all of which are offered to each machine. Around 8 PCI devices share exactly the same IRQ line (INTINA# by INTINH#) https://nathanlabsadvisory.com/ncema-7000-2015-certification/