Units Are needed to follow a protocol so that the interrupt-request (IRQ) lines may be shared. The PCI bus incorporates 4 interrupt traces, INTA# by means of INTD#, all of which can be found to each system. Approximately 8 PCI gadgets share precisely the same IRQ line (INTINA# by way https://nathanlabsadvisory.com/nist-800-cyber-security-frame-work/