Products are necessary to observe a protocol so that the interrupt-ask for (IRQ) traces may be shared. The PCI bus includes 4 interrupt traces, INTA# by INTD#, all of which can be found to each unit. Around 8 PCI equipment share the same IRQ line (INTINA# by means of INTINH#) https://nathanlabsadvisory.com/security-program-advisory/