Units Are needed to observe a protocol so that the interrupt-ask for (IRQ) lines is often shared. The PCI bus consists of 4 interrupt lines, INTA# by way of INTD#, all of which can be found to every unit. As many as 8 PCI gadgets share exactly the same IRQ https://nathanlabsadvisory.com/iso-27701-privacy-information-management-system-pims/