Units are needed to stick to a protocol so which the interrupt-ask for (IRQ) lines could be shared. The PCI bus incorporates four interrupt strains, INTA# by way of INTD#, all of which are available to every gadget. As much as 8 PCI gadgets share a similar IRQ line (INTINA# https://nathanlabsadvisory.com/cis-center-internet-security/