DDR stands for Double Data Rate RAM. The main difference between these two versions of RAM lies within the rate of data. DDR 2 is the second generation in the DDR RAM family. Is not as fast as DDR 3. It runs half the speed of the system clock. Compared to DDR 3, the bandwidth of DDR 2 is smaller. DDR 2 consumes more power than DDR
3.The distance between the left side of RAM stick and notch on DDR 2 is 7.1cm DDR 3 is the third in the family of DDR RAM. DDR 3 is twice as fast as DDR 2. The memory clock runs at a quarter speed of the system clock. DDR 3 is much more expensive than DDR 2. The distance between the left side of the RAM stick and the notch is 5.4cm.
The first thing that you have to know is that DDR stands for Double Data Ram. The DDR2 can provide 4 data transfers per cycle while the DDR3 is considered to be more advanced because it can do 8 data transfers per cycle. This means that the type of MB that will be available will increase with more advanced DDR.
If you want to make sure that you will get the best ram, you can always choose DDR3 if you want things to be faster and more advanced. You may also need bigger RAM depending on the applications that you are placing on your computer or your other gadgets.