Double Data Rate 2(DDR2) SDRAM memory is a product built upon the foundation of older DDR memory technology. DDR2 SDRAM memory can do two operations per clock cycle, just like DDR memory with speeds upto 800Mhz. By having DDR2 technology, you are increasing your memory bandwidth over the corresponding DDR SDRAM.
DDR2 is the evolution of DDR memory technology. DDR2 memory features lower power consumption, higher data bandwidths, faster speeds and enhanced thermal performance.