A mechanism receives start and done commands containing packet identifiers or sequence numbers from a packet processing engine for packets for which processing is being started and for which processing has completed respectively. Upon receiving a packet start command, an entry in an active packet list is created. Upon receiving a packet done command, the active packet list is updated. The oldest done packet in the active list is retired by flushing buffered write information to a memory system. The active packet list can be used in conjunction with a system supporting speculative reads and conflict detection. In some embodiments the packet start command is inferred from a read command containing a packet identifier or sequence number.