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Encyclopedia > GDDR2

DDR2 SDRAM (Double Data Rate Two Synchronous Dynamic Random Access Memory) is a computer memory technology that, as of 2005, is becoming the mainstream standard for personal computer memory. DDR2 is part of the SDRAM family of random access memory technologies. The terms storage (U.K.) or memory (U.S.) refer to the parts of a digital computer that retain physical state (data) for some interval of time, possibly even after electrical power to the computer is turned off. ... 2005 is a common year starting on Saturday of the Gregorian calendar. ... DRAM is a type of random access memory that stores each bit of data in a separate capacitor. ... Look up Random Access Memory in Wiktionary, the free dictionary Different types of RAM. From top to bottom: DIP, SIPP, SIMM 30 pin, SIMM 72 pin, DIMM, RIMM RAM redirects here. ...


The advantage of DDR2 over DDR-I is its ability to work at higher effective clock speeds. DDR SDRAM or double-data-rate synchronous dynamic random access memory is a type of memory integrated circuit used in computers. ... In synchronous digital electronics, such as most computers, a clock signal is a signal used to coordinate the actions of two or more circuits. ...


DDR2 represents a further doubling of the "effective" clock rate over DDR, which itself doubled the effective clock rate of SDR. With a clock frequency of 100 MHz, SDR will transfer data on every rising edge of the clock, thus achieving an effective 100 MHz transfer rate. Like DDR, DDR2 will transfer data on every rising and falling edge of the clock (double pumped), achieving an effective rate of 200 MHz. However, DDR2's bandwidth is further boosted by an increased number of buffers, improved prefetch, reduced electrical requirements, improved packaging and on-die termination. However, latency is dramatically increased as a trade-off. In computing, a double pumped computer bus transfers data on both the rising and falling edges of the clock signal, effectively doubling the data transmission rate without having to deal with the additional problems of timing skew that increasing the number of data lines would introduce. ... Latency is the time a message takes to traverse a system. ...


Power savings are achieved primarily due to the improved process technology used to manufacture chips, but also because of the slight drop in operating voltage, and the lower clock frequency used (compared to a DDR equivalent). A DDR2 product can use a clock frequency of 1/4 that of SDR, whilst maintaining approximately the same bandwidth. A lower clock frequency is both easier to route across a circuit board, and results in lower power usage, particularly when the data bus is latent.

Contents

1 The GDDR2 offshoot
2 Integration
3 Alternatives
4 External links

Chip specification

  • PC2 3200 (DDR2-400): clocked at 100MHz, data moves at 400 MHz (bandwith 3.2 GB/s)
  • PC2 4200 (DDR2-533): clocked at 133MHz, data moves at 533 MHz (bandwith 4.2 GB/s)

The following new DDR2 SDRAM specifications are currently rare, highly expensive and are only used on top-end Intel (925X or above) chipset models.

  • DDR2-600
  • DDR2-733
  • DDR2-800
  • DDR2-933
  • DDR2-1066

DDR2-SDRAM are made with the following memory amount:

  • 64 MB (rare and obsolete)
  • 128 MB (becoming rare)
  • 256 MB (lower mainstream)
  • 512 MB (upper mainstream)
  • 1024 MB (top end and expensive)

The GDDR2 offshoot

The first commercial product to claim using the "DDR2" technology was the NVIDIA GeForce FX 5800 series of graphics cards. However, it is important to note that the "DDR2" memory used on graphics cards (officially referred to as GDDR2) is not exactly the same as DDR2, but rather something of an early melding of the DDR and DDR2 technologies. In particular, the ability to transfer 4 bits of data per pin per clock cycle is missing. It had severe trouble with overheating, because nominal DDR voltages were still being used. ATI has since created the improved GDDR3 memory, which is more true to the DDR2 specifications (though with several differing features, making it better suited for graphics card use) and has largely replaced GDDR2 in graphics cards. NVIDIA Corporation (NASDAQ: NVDA) is a major supplier of graphics processors (graphics processing units, GPUs), graphics cards, and media and communications devices for PCs and game consoles (Xbox). ... The GeForce FX is a graphics card in the GeForce line, from the manufacturer NVIDIA. The fastest model (GeForce FX 5950 Ultra) appears comparable to competitor ATI Technologiess Radeon 9800 XT. It features DDR, DDR-II or GDDR-3 memory, a 130 nanometer fabrication process, and a wide swath... GDDR3 is a graphics card-specific memory technology, designed by ATI Technologies. ...


After DDR2's introduction with the GeForce FX 5800 series the 5900 series reverted to DDR, as did the 5950, but nVidia's old mainstream card, the 5700 Ultra, used DDR2 clocked at 900 MHz (compared to 800 MHz on the regular 5800 or 1GHz on the 5800 Ultra).


ATI Technologies's Radeon 9800 Pro with 256 MB memory (not the 128 MB version) also used DDR2, but this was because it required fewer pins than DDR. The Radeon 9800 Pro 256 MB only runs its memory at 20 MHz faster than the 128 MB version, primarily to counter the performance hit caused by higher latency and the increased number of chips. It is speculated that the DDR2 used on ATI's 9800 Pro 256 MB was actually supposed to be used on the GeForce FX 5800 series, but ended up unused after NVIDIA decided to halt the 5800 line's production. The 9800XT that followed reverted to DDR, and later on ATI began to use GDDR3 memory on their Radeon X800 line. ATI Technologies Inc. ... Radeon is a brand of graphics processing units (GPU) that has been manufactured by ATI Technologies since 2000. ... GDDR3 is a graphics card-specific memory technology, designed by ATI Technologies. ...


Integration

DDR2 was introduced at two initial speeds - 400 MHz (referred to as PC2-3200) and 533 MHz (PC2-4300). Both perform worse than their DDR equivalents owing to the fact that total access times are (in the worst case) twice as large. However, DDR won't officially be introduced at 533 MHz. "DDR533" RAM exists, but JEDEC has stated that such a standard won't be approved by them. These modules use significantly more power than slower modules. JEDEC stands for Joint Electron Device Engineering Council and is the semiconductor engineering standardization body of the Electronic Industries Alliance (EIA), a trade association that represents all areas of the electronics industry. ...


Currently, at least Intel supports DDR2 in their 9xx chipsets. AMD also has plans to add DDR2 support into their AMD64 processors (that all have memory controllers integrated into them) at some point in 2005 or 2006. This is a list of computer motherboard chipsets made by Intel. ... The AMD64 or x86-64 or x64 is a 64-bit processor architecture invented by AMD. It is a superset of the x86 architecture, which it natively supports. ...


Alternatives

Generally, DDR2 is expected to have little competition in main computer memory sector. However, there are three alternatives.


The first is Rambus XDR DRAM (eXtreme Data Rate DRAM). This technology can achieve very high clock speeds, but Rambus has been virtually disowned by IBM PC compatible chipset makers, and it is considered more likely that XDR will find use in set-top appliances and the like. Sony has selected XDR for use in PlayStation 3. Rambus Incorporated (NASDAQ: RMBS) (founded 1990) is a provider of high-speed interface technology, most notably their Rambus Direct RAM memory technology, which was intended to replace SDRAM as the standard memory used in computers. ... XDR DRAM is a high performance RAM with clocking in at 3. ... One of the first PCs from IBM - the IBM PC model 5150. ... Sony Corporation (Japanese katakana: ソニー) (TYO: 6758), (NYSE: SNE) is a global consumer electronics corporation based in Tokyo, Japan. ... The PlayStation 3 (colloquially known as the PS3) is the next video game console in Sony Computer Entertainments (SCEI) market-leading PlayStation series. ...


Next is Kentron Quad Band Memory (QBM), which uses DDR modules with effectively two channels routed to the module. This was briefly supported by VIA, but they have dropped support for the technology, and there are doubts about Kentron's commercial viability. VIA Technologies is a Taiwanese manufacturer of integrated circuits, mainly motherboard chipsets, CPUs, and memory, and is part of the Formosa Plastics Group. ...


The final alternative is Quad Data Rate SDRAM (QDR), which is considered the natural successor to DDR technologies (DDR2 uses some QDR transfer methods, though is still very much based on DDR technology). However, QDR is not currently considered to be even a remotely viable product due to high production costs and poor speeds currently achieved by such modules - most barely achieve 66 MHz (266 MHz effective), and the technology may not be viable until late in the decade. Quad Data Rate (QDR) SDRAM is a type of computer memory, more specifically a type of synchronous dynamic random-access memory, that can transfer four words of data in each clock cycle. ...


Finally, the yet-to-be-finalised evolution of DDR2 is... DDR-III. DDR-III is the name of the new DDR3 Standard being developed as the successor to DDR2 While DDR SDRAM processes data between 266Mbps and 400Mbps, and DDR2 between 400 Mbps and 667 Mbps, Samsung Electronics prototype which is expected to be launched in early 2006, could process data...


External links

  • Overview of DDR-II technology (http://www.lostcircuits.com/memory/ddrii/)
  • Overview of Rambus XDR (http://www.gamepc.com/labs/view_content.asp?id=xdrpreview&page=1)
  • Overview of QBM (http://www.xbitlabs.com/articles/memory/display/qbm.html)

  Results from FactBites:
 
DDR2 SDRAM - Wikipedia, the free encyclopedia (1140 words)
However, it is important to note that the "DDR2" memory used on graphics cards (officially referred to as GDDR2) is not DDR2 per se but an early midpoint of DDR and DDR2 technologies.
ATI Technologies's Radeon 9800 Pro with 256 MiB memory (not the 128 MiB version) also used GDDR2, but this was because it required fewer pins than DDR.
It is speculated that the GDDR2 used on ATI's 9800 Pro 256 MiB was actually supposed to be used on the GeForce FX 5800 series, but ended up unused after NVIDIA decided to halt the 5800 line's production.
[H] Enthusiast - GeForceFX 5700U GDDR3 (769 words)
The reason for this lack of adaptation is the fact that GDDR2 memory requires the same amount of VDD Voltage (2.5v) as DDR1.
Because GDDR2 runs internally at the same voltage as DDR1 and also runs at higher clock speeds the heat given off is very high compared to DDR1.
GDDR2 does have the advantage with VDDQ Voltage being at 1.8v versus DDR1’s VDDQ of 2.5v.
  More results at FactBites »

 
 

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