DDR SDRAM

DDR SDRAM double data rate synchronous dynamic random access memory) is a class of memory integrated circuits used in computers. It achieves nearly twice the bandwidth of the preceding SDR ("single data rate") SDRAMby double pumping (transferring data on the rising and falling edges of the clock signal) without increasing the clock frequency.

With data being transferred 64 bits at a time, DDR SDRAM gives a transfer rate of (memory bus clock rate) × 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus with a bus frequency of 100 MHz, DDR SDRAM gives a maximum transfer rate of 1600 MB/s

"Beginning in 1996 and concluding in June 2000, JEDEC developed the DDR (Double Data Rate) SDRAM specification (JESD79)."

Jedec has set standards for data rates of DDR SDRAM, divided into two parts. The first specification is for memory chips, and the second is for memory modules. As DDR SDRAM is superseded by the newer DDR2 SDRAM, the older DDR version is sometimes referred to as DDR1 SDRAM