DDR2 SDRAM

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

Comparisons

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

Chips and modules

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