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The Random Access Memory (RAM) is known as volatile memory because the data it holds is lost when the computer is switched off. RAM is primarily used to store data from the central processing unit (CPU) of a computer. Double Data Rate 2 or DDR2 RAM is an improved version of DDR memory. This technology is used for storing the data from a computer or another digital electronic device at high speeds. The DDR and the DDR2 are both types of Synchronous Dynamic Random Access Memory (SDRAM), which allows them to run faster than conventional memory.

Though DDR and DDR2 are similar, DDR2 RAM uses an upgraded technological design. This improved design allows DDR2 RAM to run faster than standard DDR memory. This modified design also provides more bandwidth, allowing more data to pass through the RAM chip at any given time, which thereby improves the performance of a computer. The DDR2, due to its improved technology, uses less power than DDR memory even though it runs faster. The DDR2 saves power through an advanced manufacturing process known as die shrinkage. This allows a drop in operating voltage (1.8V compared to the DDR’s 2.5V). The lower memory clock frequency also contributes to power reductions in applications that do not require very high speeds.

The DDR2 RAM, through its advanced technology, stores memory in memory cells and synchronizes its operations with an external data bus. The DDR2 cells use dual pumping technology to transfer data each memory cell cycle and effectively operate at twice the bus speed. In addition, off-chip drivers, on-die termination, electrical interface improvements and prefetch buffers all contribute to help boost the DDR2’s bus frequency.

For increased efficiency, the DDR2 RAM requires the chips to be assembled in a more expensive and more difficult BGA package compared to the TSSOP package of the earlier generation of memory cards such as DDR SDRAM and SDR SDRAM. This ensures that signal integrity at higher speeds is maintained.

In 2003, the DDR2 was introduced with two initial speeds: 200MHz and 266MHz. The DDR2 memory cards only started becoming popular at the end of 2004 when modules of lower latencies came out. The DDR2 dual in-line memory modules (DIMM) are not backward compatible with DDR DIMMs, due to a higher pin density (the DDR2 is a 240-pin module and the DDR is a 184-pin module). It is seen that the faster DDR2 DIMMs are compatible with slower DDR2 DIMMs, but the faster module runs at the slower module’s speed. These modules are installed in the dual in-line memory slots on the computer’s motherboard. Most of the latest motherboards provide four DIMM slots for the memory to use the fastest dual-channel mode.