Techniques for maintaining an order of transactions in a multi-bus computer architecture. In an embodiment, an arbitrator receives access requests from a plurality of requestors, each access request requesting a respective access to a bus. Based on an arbitration between the access requests—e.g. between those requestors providing the access requests—the arbitrator may generate a grant message which triggers a carrying of a first message on the first bus. In certain embodiments, the grant message further triggers another carrying of the first message on the second bus.