High-Performance QDR-IV Parallel Interface Memory with 1066 MHz Frequency and On-Die Termination for Commercial Applications The QDR™-IV XP (Xtreme Performance) SRAM is a high-performance memory device optimized to maximize the number of random transactions per second by the use of two independent bidirectional data ports. These ports are equipped with DDR interfaces and designated as port A and port B respectively. Accesses to these two data ports are concurrent and independent of each other. Access to each port is through a common address bus running at DDR. The control signals are running at SDR and determine if a read or write should be performed.