Products are needed to abide by a protocol so that the interrupt-ask for (IRQ) lines could be shared. The PCI bus involves 4 interrupt traces, INTA# through INTD#, all of which are offered to each unit. Around 8 PCI products share the exact same IRQ line (INTINA# through INTINH#) in https://nathanlabsadvisory.com/data-protection-officer-service-virtual-dpo/