double data rate


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double data rate

[¦dəb·əl ′dad·ə ‚rāt]
(computer science)
A clocking technique that increases the transfer speeds of synchronous memories by using both the leading and trailing edges of the clock signal to transfer data, effectively doubling the transfer rate or bandwidth.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

SDRAM

(Synchronous DRAM) The type of dynamic RAM memory chip in wide use since the mid-1990s. SDRAM divides the chip into two cell blocks and interleaves 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) Since 2000
DDR SDRAM doubled the data transfer rate by using both the rising and falling edges of the clock cycle, and more speed is achieved with each generation (see below).

Memory Channels
Motherboards may support one, two or four channels. More than one channel requires installing modules in a prescribed order (see image below). See GDDR.

        Clock    Transfer        DIMM        Speed      Rate         Module DDR    (MHz)     (MT/s)    (V)  Pins

 DDR5 1600-3200  3200-6400  1.1  288
 DDR4  800-1600  1600-3200  1.2  284
 DDR3  400-1200   800-2400  1.5  240
 DDR2  200-533    533-800   1.8  240
 DDR   100-200    200-400   2.5  184
 SDRAM  66-133     66-133   3.3  168


Matched Slots for Dual Channel
Dual-channel motherboards use colored sockets so that DDR memory modules are inserted in pairs. These interleaved DIMM slots support one yellow pair and one black pair.







DDR RAM Modules Are "Keyed"
This example shows the notching of three DDR generations. Modules and slots are "keyed" to prevent the wrong DDR version from being inserted. See memory module.







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 billions of bits. (Image courtesy of The MITRE Corporation Archives.)
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References in periodicals archive ?
The market has seen the progression from double data rate (DDR) to DDR2 and now DDR3 memory modules.
The GDDR4 (Graphics Double Data Rate, version 4) high-speed graphics memory chip from Samsung Electronics Co Ltd, an advanced memory technology company, has been selected for the 1GB ATI Radeon HD 2900 XT and the 256MB ATI Radeon HD 2600 XT graphics processing cards from Advanced Micro Devices (NYSE:AMD) (AMD), a provider of processing solutions.
It also includes an AGP-4X graphics interface and a double data rate SDRAM at 400 Megatransfers/second memory interface with error correcting code as an option.
PCI-SIG(R), the industry organization chartered to develop and manage PCI, PCI-X and PCI Express(TM) industry-standard I/O technologies, has selected the new Agilent tools for testing of PCI-X 2.0 for double data rate (DDR) technologies at upcoming PCI-SIG compliance workshops.
'N1 is important for Sun to stay in the game with HP and IBM but they and everybody else will have to learn to live in a world that doesn't need as many servers.' Meanwhile, Apple has announced an upgrade of its Xserve(TM) 1U rack servers through dual 1.33 GHz PowerPC G4 processors, up to 2GB of 333 MHz Double Data Rate (DDR) memory and up to 720GB of hot-plug storage.
The new 12-inch PowerBook G4 has a 867 MHz PowerPC G4 processor with Velocity Engine and offers 256MB of fast Double Data Rate (DDR) memory (expandable to 640MB) and a fast NVIDIA GeForce4 420 Go graphics processor with 32MB of dedicated DDR RAM for incredible 3D graphics and display performance.
Despite the small chassis, the S series comes with industry-standard features, including an Intel Pentium 4 processor, Double Data Rate memory, full-height PCI slots, standard optical drives, four front-access high-speed USB 2.0 ports, and front-access audio ports.
DDR stands for 'double data rate' and doubles the rate at which information in the RAM is sent to the processor.
DDR (Double Data Rate) memory, sometimes called DDR SDRAM (Double Data Rate Synchronous Dynamic Random Access Memory) or similar names, is backed by Intel archrival Advanced Micro Devices (AMD) and other companies.
Compaq is not disclosing the value of deal; or exactly what type of chips Micron is supplying but sources say that DRAM, synchronous DRAM - including the PC133 and double data rate types - Rambus DRAM and Flash memory will all be on the menu.
Mercury Systems announced the first volume production shipment of BuiltSECURE high density double data rate fourth-generation synchronous dynamic random-access memory to a leading defense prime contractor.