In an embodiment, a memory port controller (MPC) is coupled to a memory port and receives transactions from processors and a coherency port (ACP) used by one or more peripheral devices that may be cache coherent. The transactions include various quality of service (QoS) parameters. If a high priority QoS transaction is received on the ACP, the MPC may push previous (lower priority) transactions until the high priority transaction may be completed. The MPC may maintain a count of outstanding high priority QoS transactions. The L2 interface controller and ACP controller may push increment and decrement events based on processing the high priority QoS transactions, and the MPC may push the memory transactions when the count is non-zero. In an embodiment, the MPC may continue pushing transactions until the L2 interface controller informs the MPC that the earlier transactions have been completed.