DDR=Double Data Rate synchronous dynamic random access memory. Strictly speaking, DDR should be called the DDR SDRAM, people used to call a DDR, wherein, SDRAM is Synchronous Dynamic Random Access Memory abbreviation, namely synchronous dynamic random access memory. DDR SDRAM is Double Data Rate SDRAM abbreviation, is synchronous dynamic random access memory means. DDR memory is evolved in the SDRAM memory based on SDRAM production system, still in use, so as to the memory manufacturers, only on the manufacturing of common SDRAM equipment improved slightly, can realize the DDR memory production, which can effectively reduce the cost.