Units are required to observe a protocol so that the interrupt-request (IRQ) lines is often shared. The PCI bus contains 4 interrupt strains, INTA# by means of INTD#, all of which are available to each machine. Around 8 PCI equipment share precisely the same IRQ line (INTINA# via INTINH#) in https://nathanlabsadvisory.com/nerc-cip-compliance/