Products are necessary to stick to a protocol so that the interrupt-ask for (IRQ) lines may be shared. The PCI bus consists of 4 interrupt traces, INTA# by means of INTD#, all of which are available to every system. Around eight PCI equipment share a similar IRQ line (INTINA# by https://nathanlabsadvisory.com/iso-55001-2014-certification-it-asset-management/