QDR"-II stands for Quad Data Rate"-II and is a name that best describes the functionality of the new architecture. By allowing two ports to run independently at Double Data Rate, the net result is four data items per clock cycle, or Quad Data Rate. The QDR"-II has additional features, which differentiate it from the QDR SRAM. The major differences are the addition of a DLL on the QDR"-II, an extra half cycle of latency, extended data valid window on the QDR"-II and presence of echo clocks. For more information, please refer to the QDRII/DDRII Design Guidelines application note attached here.