Editing Dynamic random-access memory (section)

====Double data rate synchronous DRAM====
{{Main|DDR SDRAM|DDR2 SDRAM|DDR3 SDRAM|DDR4 SDRAM|DDR5 SDRAM}}
[[File:SAMSUNG@DDR-SDRAM@64MBit@K4D62323HA-QC60 Stack-DSC03539-DSC03556 - ZS-DMap.jpg|thumb|The [[die (integrated circuit)|die]] of a Samsung DDR-SDRAM 64-MBit package]]
Double data rate SDRAM (DDR SDRAM or DDR) was a later development of SDRAM, used in PC memory beginning in 2000. Subsequent versions are numbered sequentially (''DDR2'', ''DDR3'', etc.).  DDR SDRAM internally performs double-width accesses at the clock rate, and uses a [[double data rate]] interface to transfer one half on each clock edge.  DDR2 and DDR3 increased this factor to 4× and 8×, respectively, delivering 4-word and 8-word bursts over 2 and 4 clock cycles, respectively.  The internal access rate is mostly unchanged (200 million per second for DDR-400, DDR2-800 and DDR3-1600 memory), but each access transfers more data.