What is meant by DDR RAM ?

DDR stands for Double Data Rate.

Double Data Rate Random access memory (DDR RAM), is mush faster then the SDRAM, Synchronous Dynamic Random Access Memory.

DDR RAM has the speed of twice as that of the SDRAM.

The DDR RAM has the speed twice as that of SDRAM because , SDRAM uses the rising part of the clock chip cycle to transfer data, whereas DDR RAM uses the rising and falling regions of the clock chip cycle to transfer data.