The DDR standard was superseded in 2003 by DDR2, a memory standard offering greater speeds and lower power consumption than its predecessor. The difference between DDR and DDR2 is important if you're looking to service your computers, as the two standards are not physically compatible with each other. read more
The key difference between DDR and DDR2 is that in DDR2 the bus is clocked at twice the speed of the memory cells, so four words of data can be transferred per memory cell cycle. Thus, without speeding up the memory cells themselves, DDR2 can effectively operate at twice the bus speed of DDR. read more
As such, DDR2 chips cannot be used in the memory slots of a machine designed to take DDR memory, and vice versa. As a result of these physical differences, double-check your computer's memory type before purchasing new memory. read more
DDR2 memory at the same clock speed as DDR will provide the same bandwidth but markedly higher latency, providing worse performance. DDR3 memory reduces 40% power consumption compared to current DDR2 modules, allowing for lower operating currents and voltages (1.5 V, compared to DDR2`s 1.8 V or DDR`s 2.5 V). read more