A peripheral device includes a bus interface and circuitry. The bus interface is to exchange bus transactions over a peripheral bus that permits out-of-order transfer of at least some of the bus transactions. The circuitry is to generate a plurality of streams of the bus transactions, to select, from among the plurality of streams, one or more streams for which transaction ordering is required, to enforce the transaction ordering among the bus transactions of the selected streams, and to send the bus transactions via the bus interface to the peripheral bus.