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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DDR2 was in turn superseded by DDR3 SDRAM, which offered higher performance for increased bus speeds and new features. DDR3 has been superseded by DDR4 SDRAM, which was first produced in 2011 and whose standards were still in flux (2012) with significant architectural changes. DDR's prefetch buffer depth is 2 (bits), while DDR2 uses 4.
However, it can open two memory pages at once, which simulates the dual-port nature of other video RAM technologies. The earliest known SGRAM memory are 8 Mbit [ 6 ] chips dating back to 1994: the Hitachi HM5283206, introduced in November 1994, [ 34 ] and the NEC μPD481850, introduced in December 1994. [ 35 ]
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 ...
(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 clock I/O bus clock Transfer rate Theoretical bandwidth DDR-200, PC-1600 100 MHz 100 MHz 200 MT/s 1.6 GB/s DDR-400, PC-3200 200 MHz 200 MHz 400 MT/s 3.2 GB/s DDR2-800, PC2-6400 200 MHz 400 MHz 800 MT/s 6.4 GB/s DDR3-1600, PC3-12800 200 MHz 800 MHz 1600 MT/s 12.8 GB/s DDR4-2400, PC4-19200 300 MHz 1200 MHz 2400 MT/s 19.2 GB/s
A DIMM (Dual In-Line Memory Module) is a popular type of memory module used in computers. It is a printed circuit board with one or both sides (front and back) holding DRAM chips and pins . [ 1 ] The vast majority of DIMMs are manufactured in compliance with JEDEC memory standards , although there are proprietary DIMMs.
Memory timings or RAM timings describe the timing information of a memory module or the onboard LPDDRx. Due to the inherent qualities of VLSI and microelectronics, memory chips require time to fully execute commands. Executing commands too quickly will result in data corruption and results in system instability.