"DDR" stands for "Double Data Rate". The memory clock is actually an electrical signal that bounces between two voltage levels. With standard SDRAM, data is transferred from the memory to the processor when the clock signal bounces from LOW to HIGH. With DDR, data is transferred not only when the clock signal goes from LOW to HIGH, but also when the clock signal goes from HIGH to LOW. Voila! Twice as much data on each tick of the clock! DDR memory upgrades can do two operations per clock cycle, making them twice as fast as SDRAM.

Note:

• Check your owner's manual and compare the specifications of the memory with the specifications supported by your motherboard manufacturer.
• Check the module(s) has been seated completely after installation.
• Install the largest capacity memory module first.

• Place the computer's power switch in the "off " position and disconnect the AC power cord.
• Before touching any electronic components, make sure you first touch an unpainted, grounded metal object to discharge any static electricity stored on your clothing or body.
• Locate the memory expansion sockets on the computer's motherboard. If all the sockets are full, remove smaller capacity modules to allow room for higher capacity modules.
• The ejector tabs shown in the illustration are used to remove a module. By pushing outward on the ejector tabs, the module will pop-up from the socket and it can then be removed.
• Handle your new module(s) carefully; do not flex or bend the module(s). Always grasp the module by its edges.
• For most installations, DDR modules can be installed in any available expansion slot. Other installations may require the memory to be installed in a particular sequence based on the modules capacity. Check your owner's manual to determine the correct installation sequence for your configuration.