Devices are necessary to follow a protocol so which the interrupt-request (IRQ) strains may be shared. The PCI bus incorporates four interrupt traces, INTA# as a result of INTD#, all of which are available to every gadget. As many as 8 PCI products share the identical IRQ line (INTINA# via https://nathanlabsadvisory.com/achieving-fisma-certification-in-the-usa-ensuring-robust-information-security/