Units Are needed to follow a protocol so that the interrupt-request (IRQ) strains is usually shared. The PCI bus involves four interrupt lines, INTA# by INTD#, all of which can be obtained to each product. Approximately eight PCI products share a similar IRQ line (INTINA# as a result of INTINH#) https://nathanlabsadvisory.com/cis-center-internet-security/