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Double Data Rate 2 Synchronous Dynamic Random-Access Memory (DDR2 SDRAM) is a double data rate (DDR) synchronous dynamic random-access memory (SDRAM) interface. It is a JEDEC standard (JESD79-2); first published in September 2003. [2] DDR2 succeeded the original DDR SDRAM specification, and was itself succeeded by DDR3 SDRAM in 2007.
DDR2 started to be effective by the end of 2004, as modules with lower latencies became available. [19] Memory manufacturers stated that it was impractical to mass produce DDR1 memory with effective transfer rates in excess of 400 MHz (i.e. 400 MT/s and 200 MHz external clock) due to internal speed limitations.
(memory density) This is the total memory capacity of the chip. Example: 128 Mib. (memory depth) × (memory width) Memory depth is the memory density divided by memory width. Example: for a memory chip with 128 Mib capacity and 8-bit wide data bus, it can be specified as: 16 Meg × 8. Sometimes the "Mi" is dropped, as in 16×8.
Memory controller with differential serial connections to DDR2 FB-DIMMs. The AMB is visible in the center of each DIMM. A Fully Buffered DIMM (FB-DIMM) is a type of memory module used in computer systems. It is designed to improve memory performance and capacity by allowing multiple memory modules to be each connected to the memory controller ...
Dynamic random-access memory (dynamic RAM or DRAM) is a type of random-access semiconductor memory that stores each bit of data in a memory cell, usually consisting of a tiny capacitor and a transistor, both typically based on metal–oxide–semiconductor (MOS) technology. While most DRAM memory cell designs use a capacitor and transistor ...
DRAM load on the command/address (CA) bus can be reduced by using registered memory. [citation needed] Predating the term rank (sometimes also called row) is the use of single-sided and double-sided modules, especially with SIMMs. While most often the number of sides used to carry RAM chips corresponded to the number of ranks, sometimes they ...
In March 2008 DIMM prices are about half ($30/GB), while DDR2 prices are about one quarter ($15/GB) - and the price drop for SO-DIMMs is much less than for DIMM ($50/GB), while the DDR2 prices for SO-DIMM are almost the same ($16/GB). Thus I wonder whether DDR2 is in mass production nowadays and DDR is out of production, but remaining stock only.
To emphasize the advantages of the DDR technique, this type of RAM was marketed at speeds twice the actual clock rate, i.e. the 400 MHz Rambus standard was named PC-800. This was significantly faster than the previous standard, PC-133 SDRAM , which operated at 133 MHz and delivered 1066 MB/s of bandwidth over a 64-bit bus using a 168-pin DIMM ...