DDR SDRAM

DDR SDRAM

Double data rate (DDR) SDRAM memory is an evolutionary design of standard SDRAM in which data is transferred twice as quickly. Instead of doubling the actual clock rate, DDR memory achieves the doubling in performance by transferring twice per transfer cycle: once at the leading (falling) edge and once at the trailing (rising) edge of the cycle. DDR SDRAM uses a new DIMM module design with 184 pins. DDR DIMMs are rated for either PC1600 (200MHz x 8) or PC2100 (266MHz x 8) operation or normally run on 2.5 volts. They are basically an extension of the PC100 and PC133 DIMMs redesigned to support double clocking, where data is sent on each clock transition (twice per cycle) rather than once per cycle as with standard SDRAM.

A typical DDR SD RAM