Products Are needed to adhere to a protocol so the interrupt-request (IRQ) strains could be shared. The PCI bus consists of 4 interrupt lines, INTA# through INTD#, all of which are offered to each product. Around 8 PCI devices share the same IRQ line (INTINA# by way of INTINH#) in https://nathanlabsadvisory.com/pci-3ds/