A method for synchronizing messages between processors is provided. The method comprising receiving, by a first external device, inbound messages for applications running redundantly in high integrity mode on two or more multi-core processors. The inbound messages are synchronously copied to the multi-core processors. The multi-core processors send outbound messages to respective alignment queues in the first external device or a second external device, wherein the outbound messages contain calculation results from the inbound messages. The first or second external device compares the alignment queues. Matched outbound messages in the alignment queues are sent to a network or data bus. Any unmatched outbound messages in the alignment queues are discarded.