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In 2003, the JEDEC standards organization presented Samsung with its Technical Recognition Award for the company's efforts in developing and standardizing DDR2. [1] DDR2 was officially introduced in the second quarter of 2003 at two initial clock rates: 200 MHz (referred to as PC2-3200) and 266 MHz (PC2-4200).
The standards specify the physical and electrical characteristics of the modules, and include the data for computer simulations of the memory module operating in a system. [10] Memory modules of the DDR2-SDRAM type are available for laptop, desktop, and server computers in a wide selection of capacities and access speeds.
DDR SDRAM specification was finalized by JEDEC in June 2000 (JESD79). [9] JEDEC has set standards for the data rates of DDR SDRAM, divided into two parts. The first specification is for memory chips, and the second is for memory modules. The first retail PC motherboard using DDR SDRAM was released in August 2000. [10]
JEDEC formally adopted its first SDRAM standard in 1993 and subsequently adopted other SDRAM standards, including those for DDR, DDR2 and DDR3 SDRAM. SDRAM is also available in registered varieties, for systems that require greater scalability such as servers and workstations.
The full memory timings of a memory module are stored inside of a module's SPD chip. On DDR3 and DDR4 DIMM modules, this chip is a PROM or EEPROM flash memory chip and contains the JEDEC-standardized timing table data format.
The maximum time interval between refresh operations is standardized by JEDEC for each DRAM technology and is specified in the manufacturer's chip specifications. It is usually in the range of milliseconds for DRAM and microseconds for eDRAM. For DDR2 SDRAM chips it is 64 ms.
The term rank was created and defined by JEDEC, the memory industry standards group. On a DDR, DDR2, or DDR3 memory module, each rank has a 64-bit-wide data bus (72 bits wide on DIMMs that support ECC). The number of physical DRAMs depends on their individual widths.
The DDR3 JEDEC standard for VLP DIMM height is around 0.740 inches (18.8 mm). These will fit vertically in ATCA systems. Full-height 240-pin DDR2 and DDR3 DIMMs are all specified at a height of around 1.18 inches (30 mm) by standards set by JEDEC. These form factors include 240-pin DIMM, SO-DIMM, Mini-DIMM and Micro-DIMM. [16]