Some features of DDR RAM include faster data and transfer rates and a lower voltage requirement. DDR1 RAM has a prefetch buffer width of 2-bits.
DDR1 RAM is twice the speed of SDR RAM. This speed increase is mostly because DDR RAM can transfer data on the up and down tick of a CPU clock. DDR RAM also benefits from having direct communication with the CPU northbridge as opposed to going through a separate memory controller, though this benefit is not exclusive to DDR. The voltage requirement of DDR1 memory is around 2.6v, which is quite lower than the 3.3v of SDR RAM.