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(Synchronous DRAM) The type of dynamic RAM memory chip that has been widely used since the mid-1990s. SDRAM eliminated wait states by dividing the chip into two cell blocks and interleaving data between them. While a bit in one block is accessed, a bit in the other is prepared for access. See dynamic RAM.

DDR (Double Data Rate)
In 2000, DDR SDRAM doubled the data transfer rate by using both the rising and falling edges of the clock cycle. The data rate of each DDR generation is faster than the previous with a six-fold increase from DDR1 to DDR4. In addition, less power is required (see table below). In order to prevent inserting the wrong DDR into the motherboard, DDR memory modules are keyed differently (for details, see memory module).

Chipsets on the motherboard may support one, two or four memory channels (triple channel has since come and gone). For example, mainstream motherboards support dual channel, which is why memory modules are generally installed in pairs. While data are being read or written to one memory module, the second module is being prepared for reading or writing. High-end motherboards support quad channel. See SGRAM.


  Following are the most popular memory
  module speeds for each SDRAM generation.

       Memory Speed   DIMM   Voltage          (MHz)      Module  Required

  DDR4     2400     284-pin   1.2
  DDR4     2133     284-pin   1.2

  DDR3     1866     240-pin   1.35/1.5
  DDR3     1600     240-pin   1.35/1.5
  DDR3     1333     240-pin   1.35/1.5

  DDR2      800     240-pin   1.8/2.5

  DDR       400     184-pin   2.5

  SDRAM     133     168-pin   3.3
  SDRAM     100     168-pin   3.3

Matched Slots for Dual Channel
This motherboard uses colored sockets so that module pairs are inserted properly. It supports three pairs (one orange and two lavender). (Image courtesy of Giga-byte Technology Company Ltd.,

A Little Nostalgia
These 12 bits of magnetic core memory from the Whirlwind computer of the early 1950s take up about a quarter of a square inch. Today, that much space holds hundreds of millions of bits. (Image courtesy of The MITRE Corporation Archives.)
References in periodicals archive ?
But prices for SDRAM, while still at historically low levels, may be headed back up, while Rambus says prices for its technology are falling.
The SDRAM upgrades are manufactured in accordance with 168-pin JEDEC standards.
The SDRAM market will begin showing its potential this year," commented Jim McGregor, senior analyst at In-Stat.
The core is available as a single port SDRAM controller or a multi-port SDRAM controller with different bus interfaces at different bus clock speed sharing the same memory.
Samsung is totally committed to serving our customers by being first-to-market with leading-edge DDR SDRAM memory products.
Production of DDR2 SDRAM using 70nm processing has already started, and the first product shipments are expected to begin in the first quarter of 2007.
In addition to the affected Kayak XM600 SDRAM models, HP has halted shipments of its XU800 SDRAM models, which contain the Intel 840 chip set, pending further testing by HP and Intel.
The integration of the ChipX DDR/DDR2 PHY with the Northwest Logic DDR and DDR2 memory controllers provides a high-performance, easy-to-use SDRAM solution," said Brian Daellenbach, President of Northwest Logic.
In addition to the new 4Mx16 (64Mb) DDR device, Hyundai offers a 1Mx16 SDRAM device which operates at frequencies up to 200MHz.
While the individual components required to build a DDR2 memory interface are available, a complete solution requires significant system-level knowledge of DDR2 SDRAM operation as well as an understanding of package design considerations and signal integrity," said Prasad Subramaniam, vice president of Design Technology, eSilicon.
Based on a completely embedded hardware architecture and solid state SDRAM memory, Anvil is the industry's first storage subsystem capable of properly addressing the technical challenges of recording real time sensor signals.
Leveraging its expertise in deep sub-micron design and packaging technology, Samsung has stacked together a highly integrated 300MHz ARM9-based mobile application processor with a memory multi-chip package (MCP), which contains high-density NAND Flash and low-power mobile SDRAM.