What is the difference between DDR and DDR2 RAM?

Answer 1

Most desktops and notebooks use one of the three most popular types of synchronous dynamic random access memory (SDRAM) for the main system memory. Single data rate (SDR) SDRAM is the older type of memory, commonly used in computers prior to 2002. Double data rate (DDR) SDRAM hit the mainstream computer market around 2002, and DDR2-based systems hit the market in mid-2004.

DDR SDRAM is a straightforward evolution from SDR SDRAM. The big difference between DDR SDRAM and SDR SDRAM is that DDR reads data on both the rising and falling edges of the clock signal, so the DDR module can transfer data twice as fast as SDR SDRAM.

While DDR has a limited clock rate, the evolutionary changes to DDR architecture enable DDR2 to achieve speeds beyond of DDR, delivering bandwidth of 5.3 GB per second and beyond! Because DDR2 is able to operate with faster bus speeds, your memory doesn't hold back the performance of your processor.

Generally speaking, motherboards are built to support only one type of memory. You cannot mix and match SDRAM, DDR, or DDR2 memory on the same motherboard in any system. They will not function and will not even fit in the same.

Answer 2

The key difference between DDR and DDR2 is that in DDR2 the bus is clocked at twice the speed of the memory cells, so four words of data can be transferred per memory cell cycle. Thus, without speeding up the memory cells themselves, DDR2 can effectively operate at twice the bus speed of DDR.

DDR2 is a 240-pin module, DDR is a 184-pin module.

DDR2 gets double speed that DDR.

Standard name Memory clock Cycle time I/O Bus clock Data transfers per second Module name Peak transfer rate DDR2-400 100 MHz 10 ns 200 MHz 400 Million PC2-3200 3.200 GB/s DDR2-533 133 MHz 7.5 ns 266 MHz 533 Million PC2-4200 4.264 GB/s DDR2-667 166 MHz 6 ns 333 MHz 667 Million PC2-53001 5.336 GB/s DDR2-800 200 MHz 5 ns 400 MHz 800 Million PC2-6400 6.400 GB/s DDR2-1066 (planned) 266 MHz 3.75 ns 533 MHz 1066 Million PC2-8500 (planned) 8.500 GB/s