What is the difference between DDR2 and DDR3 memory?

[certforumz]

What is the difference between DDR2 and DDR3 memory?
Also see: Do I need DDR2 or DDR3 memory?

DDR3 is the latest-generation memory available at Crucial. It is the successor to DDR2 memory.

Technically speaking, there are many differences between DDR2 and DDR3 memory. Electrically, DDR3 works quite a bit differently than DDR2 and also runs at 1.5v instead of DDR2's 1.8v. The benefit? This lower voltage can result in lower power consumption at comparable speeds.

From a speed (or frequency) perspective, DDR3 picks up where DDR2 leaves off. DDR2 "JEDEC standard*" memory typically stops at around 800MHz whereas DDR3 memory starts at 800MHz—although most DDR3 memory that is available today runs at 1066MHz and 1333MHz. And 1600MHz is on the horizon. Performance DDR3 memory modules (also called overclocking memory) are already running at over 2000MHz.

DDR2 and DDR3 memory modules differ physically as well. While they both have similar numbers of pins, the notch in the card (or PCB) is in different locations. That means a DDR3 memory module cannot be placed in a DDR2 memory socket and vice-versa.

*JEDEC, which stands for Joint Electron Devices Engineering Council, is the independent standards body that works with DRAM manufacturers to develop and publish the specifications that define how memory works. Micron, Crucial's parent company, is a member of JEDEC and sits on the Board of Directors for the organization

http://www.crucial.com/support/difference_ddr2_ddr3.aspx