DDR3 SDRAM

Third generation DDR memory leaps greatly forward in data transfer rate and power management. DDR3 provides even higher bandwidth than DDR2 due to the 8-bit prefetch buffer (4-bit prefetch of DDR2, and 2-bit of DDR). The advanced fabrication technology allows lower operating currents and voltages (1.5V, compared to 1.8V of DDR2) and thus enhances thermal performance. Successor to DDR2, DDR3 is considered to replace DDR and DDR2 in coming years. DDR3 memory modules take the form of 240-pin DIMMs, and are not compatible with DDR2 memory slots.

DDR2 SDRAM

Second generation DDR memory provides greater bandwidth and other new features such as On-Chip Termination (OCT). 4 bits of data are moved from the memory array to the I/O buffers (per data line) each core cycle. This can be described as 4-bit prefetch, as opposed to the single-bit fetch in SDRAM and 2-bit prefetch with DDR SDRAM. DDR2 is the dominant mainstream system memory product today, and is replacing DDR in the desktop DRAM market. DDR2 memory modules are 240-pin DIMMs.

DDR SDRAM

Double Data Rate SDRAM: DDR SDRAM sends and receives data twice as often as common SDRAM. This is achieved by transferring data on both the rising edge and the falling edge of a clock cycle. DDR memory is being phased out and replaced by DDR2 memory. DDR memory modules usually take the form of 184-pin DIMMs.