Difference between DDR2 And DDR3

 DDR2 and DDR3 RAM module

physical appearance-  They are of the same length (~13.3 cm or 5.25 in) and have the same number of pins (240): - DDR2 and DDR3 RAM looks  largely similar

In short, DDR2 and DDR3 RAM are not compatible with each other: If your motherboard has DDR2 RAM slots, then you can only use DDR2 RAM. The same applies to DDR3 RAM.

The Difference between DDR2 and DDR3 RAM.

Number of Pins Clock Speed Max Transfer Rate Voltage

DDR2 RAM 240 pins 400 to 1,066 MHz 3,200 to 8,533 MB/s 1.8V

DDR3 RAM 240 pins 800 to 2,133 MHz 6,400 to 17,067 MB/s 1.5V

The difference in clock speed and max transfer rate numbers look impressive on paper, but DDR3 RAM is in fact just 2 to 10% faster than DDR2 RAM for most real-world applications (depending on your hardware specification and usage).From the DDR2 and DDR3 table above, we can see that DDR3 RAM offers better performance while consuming less power.

DDR3 RAM consumes less power and produces less heat than DDR2 RAM at the same clock speed (e.g. DDR3 and DDR2 RAM that is both running at 1,066 MHz). However there is a catch: RAM with higher clock speeds have higher power consumption so DDR3 RAM running at 2,133 MHz will still drain more power than DDR2 RAM at 1,066 MHz.