DDR doubles the bandwidth available to your system and runs twice as fast as regular SDRAM. DDR SDRAM works very similar to SDR except that data transactions are performed at both the rising and falling edge of the clock cycle enabling DDR to literally double the data transfer rate of the original bus clock. For example; with DDR SDRAM, a system running with a clock of 100 or 133MHz will yield an effective data rate of 200 or 266 mega-transfers per second (MTS), doubling the data rate.

DDR is a technology supported by a newer generation of DRAM controllers with DDR enabled logic. DDR DIMM modules are available in a variety of form factors including 184 pin full-sized DIMM, 200 pin So-DIMM, and 184 pin Very Low Profile (VLP) DIMM. These form factors are not interchangeable with the preceding SDRAM or succeeding DDR2 technology form factors.