Units are necessary to comply with a protocol so that the interrupt-request (IRQ) strains is usually shared. The PCI bus consists of 4 interrupt strains, INTA# through INTD#, all of which are available to every device. Nearly 8 PCI devices share the identical IRQ line (INTINA# by way of INTINH#) https://nathanlabsadvisory.com/eu-us-privacy-shield-gdpr/