What Is the Difference Between DDR4, DDR3, DDR2, DDR, and SDRAM?

Most desktops and notebooks use one of several popular types of dynamic random access memory (DRAM) 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 is a straightforward evolution from SDR SDRAM. The most significant difference between DDR and SDR is that DDR reads data on both the rising and falling edges of the clock signal, enabling a DDR memory module to transfer data twice as fast as an SDR memory module.

Systems implementing the follow up technology to DDR, called DDR2,  began to appear in mid-2004. DDR2 achieves speeds beyond that of DDR, delivering bandwidth of up to 8.5 GB per second. Frequently, DDR2-based systems can use memory installed in pairs to run in "dual channel mode" to increase memory throughput even further.

DDR3 and DDR4 represent further improvements in memory technology, with improvements in bandwidth as well as power consumption, leading to better performance and stability as time went on and the standards evolved.

Generally speaking, motherboards are built to support only one type of memory. You cannot mix and match SDRAM, DDR, DDR2, DDR3, or DDR4 memory on the same motherboard in any system. They will not function and will not even fit in the same sockets.

The right type of memory to use is the one that your computer is compatible with! The easiest way to find the right memory for your computer is to look up your system with the Crucial® Advisor™ tool. The Crucial® Advisor™ tool will list only compatible memory for your system.

If you don't know the exact model of your computer, the System Scanner tool can scan your computer hardware to automatically detect your system configuration and give you a report on which upgrade is right for you.