Comparison Between DDR2 RAM and DDR RAM

DDR2 is a type of an SDRAM, this computer memory stores its memory in memory cells. These cells are then activated at according times to correctly operate with an external data bus. Although the DDR2 shares many similarities with the original DDR, as in the case with data transfer happening with the rise and fall at the edge of the clock, it is different in that the DDR2's bus is clocked at twice the speed. This basically allows the DDR2 to be twice as more efficient than the original DDR.

The key behind the high bus frequency with DDR2s is the coalition of electrical interface improvements, prefetch buffers, and various off-chip drivers. This is because DDR's prefetch buffer is twice of the DDR, which is 2bits deep. Also, its read latencies are between four and six cycles; again this is twice that of the DDR. Thus, twice as much bus speed is necessary to achieve an equal latency.

Also, the DDR2 RAM Memory is packaged relatively more expensively and more complicatedly than the DDR SDRAM or the SDR SDRAM, in exchange for a more blazing speed.

Backward compatibility with DDR2 DIMMs are quite limited. In fact, they are not designed to be compatible with DDRM DIMMs at all. This is because firstly, the notch positions in the DDR2 and the DDR are different along with the pin density slightly higher on the DDR DIMMs. Although not much of a "backward compatibility," but faster DDR2 DIMMs can be used with slower DDR2 DIMMs. However, in such a situation, the faster one would run at the speed of the slower DDR2.

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