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In information technologies we use the term DDR2 SDRAM for a Double Data Rate memory module of the second generation. This technology is used for high speed storage of the working data.

History[change | change source]

DDR2 was first made in 2001.

Comparisons[change | change source]

The main difference between DDR and DDR2 modules is that the bus on which the DDR2 memory modules are working is clocked at twice the speed of the memory cells. In practical terms we can say that four words of data can be transferred during one memory cell cycle. To sum it up DDR2 can effectively operate at twice the bus speed of DDR.

Specification standards[change | change source]

Chips and modules[change | change source]

For use in PCs, DDR2 SDRAM is supplied in DIMMs with 240 pins and a single locating notch. DIMMs are identified by their peak transfer capacity (often called bandwidth).

Standard name Memory clock Cycle time I/O Bus clock Data transfers per second Module name Peak transfer rate
DDR2-400 100 MHz 10 ns 200 MHz 400 Million PC2-3200 3200 MB/s
DDR2-533 133 MHz 7.5 ns 266 MHz 533 Million PC2-4200 4266 MB/s
DDR2-667 166 MHz 6 ns 333 MHz 667 Million PC2-5300 5333 MB/s
DDR2-800 200 MHz 5 ns 400 MHz 800 Million PC2-6400 6400 MB/s
DDR2-1066 266 MHz 3.75 ns 533 MHz 1066 Million PC2-8500 8533 MB/s