An upgrade to the DDR SDRAM standard that sometimes is called DDR2 RAM. It includes the following modules: DDR2-400, DDR2-533, DDR2-667, DDR2-800, and DDR2-1000. DDR2 uses 240-pin DIMMs and is not compatible with DDR; however, the higher-end (faster) DDR2 modules are backward compatible with the slower DDR2 modules.