Devices are needed to follow a protocol so which the interrupt-request (IRQ) lines may be shared. The PCI bus involves four interrupt strains, INTA# through INTD#, all of which can be found to each product. Nearly 8 PCI units share the identical IRQ line (INTINA# through INTINH#) in APIC-enabled x86 https://nathanlabsadvisory.com/how-soc-2-compliance-protects-your-usa-business-from-cyber-attacks/