Equipment are needed to comply with a protocol so which the interrupt-ask for (IRQ) strains might be shared. The PCI bus features 4 interrupt strains, INTA# through INTD#, all of which are available to every machine. Around 8 PCI products share a similar IRQ line (INTINA# via INTINH#) in APIC-enabled https://nathanlabsadvisory.com/iso-27001-information-security/