Devices are needed to stick to a protocol so the interrupt-ask for (IRQ) lines is often shared. The PCI bus features 4 interrupt traces, INTA# as a result of INTD#, all of which are offered to each unit. Nearly 8 PCI equipment share the same IRQ line (INTINA# by INTINH#) https://nathanlabsadvisory.com/supply-chain-security/