Units are required to follow a protocol so which the interrupt-request (IRQ) lines can be shared. The PCI bus consists of 4 interrupt traces, INTA# by means of INTD#, all of which are available to every unit. Around eight PCI equipment share a similar IRQ line (INTINA# by INTINH#) in https://nathanlabsadvisory.com/sama-compliance-saudi-arabia/