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Encyclopedia > DDR2 SDRAM
DRAM types

In electronic engineering, DDR2 SDRAM or double-data-rate two synchronous dynamic random access memory is a random access memory technology used for high speed storage of the working data of a computer or other digital electronic device. {{Mergeto ... Dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor within an integrated circuit. ... DRAM is a type of random access memory that stores each bit of data in a separate capacitor. ... DRAM is a type of random access memory that stores each bit of data in a separate capacitor. ... DRAM is a type of random access memory that stores each bit of data in a separate capacitor. ... SDRAM means synchronous dynamic random access memory which is a type of solid state computer memory. ... SDRAM means synchronous dynamic random access memory which is a type of solid state computer memory. ... DDR SDRAM or double-data-rate synchronous dynamic random access memory is a type of memory integrated circuit used in computers. ... In electronic engineering, DDR3 SDRAM or double-data-rate three synchronous dynamic random access memory is a random access memory technology used for high speed storage of the working data of a computer or other digital electronic devices. ... Direct Rambus DRAM or DRDRAM (sometimes just called Rambus DRAM or RDRAM) is a type of synchronous dynamic RAM, designed by the Rambus Corporation. ... XDR DRAM is a high performance RAM Interface like SDR-SDRAM and DDR-SDRAM. The XDR solution was engineered to be effective in small high-bandwidth consumer systems, high-performance main memory applications, and flagship GPUs. ... XDR-II DRAM is a high performance type of Dynamic Random Access Memory that is in development by Rambus. ... Virtual Channel Random Access Memory (VC-RAM in short, other names such as VC-SDRAM, VCSDRAM, VCDRAM, or VCM) was a proprietary type of SDRAM produced by NEC which NEC called it as an open standard, with no licensing fees associated with VCM. VCM creates a state in which the... VRAM an acronym for Video RAM. Generally a term used in computers to describe RAM dedicated to the purpose of displaying bitmap graphics in raster graphics hardware. ... Dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor within an integrated circuit. ... Synchronous Graphics random accsess memory SGRAM is based on SDRAM, but includes graphics-specific read/write functions SGRAM also retrieves blocks of data and so reduces the number of reads and writes that memory must carry out. ... 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. ... GDDR3 (Graphics Double Data Rate, version 3) is a graphics card-specific memory technology, designed by ATI Technologies. ... This article does not cite any references or sources. ... GDDR5 (Graphics Double Data Rate, version 5) is a type of graphics card memory. ... Electronic discipline that deals with the behavior and effects of electrons (as in electron tubes and transistors) and with electronic devices, systems, or equipment. ... In computing, a computer bus operating with double data rate transfers data on both the rising and falling edges of the clock signal. ... Several SDRAM ICs on a DIMM package. ... RAM redirects here. ... This article is about the machine. ... A digital circuit that acts as a binary clock, hand-wired on a series of breadboards Digital electronics are electronics systems that use digital signals. ...


It is a part of the SDRAM (synchronous dynamic random access memory) family of technologies, which is one of many DRAM (dynamic random access memory) implementations, and is an evolutionary improvement over its predecessor, DDR SDRAM. SDRAM means synchronous dynamic random access memory which is a type of solid state computer memory. ... Dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor within an integrated circuit. ... DDR SDRAM or double-data-rate synchronous dynamic random access memory is a type of memory integrated circuit used in computers. ...


Its primary benefit is the ability to operate the external data bus twice as fast as DDR SDRAM. This is achieved by improved bus signaling, and by operating the memory cells at half the clock rate (one quarter of the data transfer rate), rather than at the clock rate as in the original DDR. DDR2 memory at the same clock speed as DDR will provide the same bandwidth but markedly higher latency, providing worse performance. In telecommunication, signalling (UK spelling) or signaling (US spelling) has the following meanings: The use of signals for controlling communications. ... SDRAM latency refers to the delays incurred when a computer tries to access data in SDRAM. SDRAM latency is often measured in memory bus clock cycles. ...

Contents

Overview

A 512 MB DDR2 533 module with BGA chips. DDR2 is a 240-pin module (DDR2 SODIMMs are 200-pin (not shown))

Like all SDRAM implementations, DDR2 stores memory in memory cells that are activated with the use of a clock signal to synchronize their operation with an external data bus. Like DDR before it, DDR2 cells transfer data both on the rising and falling edge of the clock (a technique called "dual pumping"). The key difference between DDR and DDR2 is that in DDR2 the bus is clocked at twice the speed of the memory cells, so four bits of data can be transferred per memory cell cycle. Thus, without speeding up the memory cells themselves, DDR2 can effectively operate at twice the bus speed of DDR. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... For the Bulgarian Go Association, see Bulgarian Go Association. ... SO DIMM is an abbreviation for Small Outline Dual In-line Memory Module, and is a smaller form of DIMM used most often in notebook/portable computers, small form-factor computers (Such as those with a Mini ITX motherboard) and high-end upgradable office printers. ... In electronics and especially synchronous digital circuits, a clock signal is a signal used to coordinate the actions of two or more circuits. ... In computing, a computer bus operating with double data rate transfers data on both the rising and falling edges of the clock signal. ... In computer architecture, a bus is a subsystem that transfers data or power between computer components inside a computer or between computers and typically is controlled by device driver software. ...


DDR2's bus frequency is boosted by electrical interface improvements, on-die termination, prefetch buffers and off-chip drivers. However, latency is greatly increased as a trade-off. The DDR2 prefetch buffer is 4 bits deep, whereas it is 2 bits deep for DDR and 8 bits deep for DDR3. While DDR SDRAM has typical read latencies of between 2 and 3 bus cycles, DDR2 may have read latencies between 4 and 6 cycles. Thus, DDR2 memory must be operated at twice the bus speed to achieve the same latency. The prefetch buffer is a memory cache located on modern RAM modules which stores data before it is actually needed. ... In computing, memory latency is the time between initiating a request for a byte or word in memory until it is retrieved. ...


Another cost of the increased speed is the requirement that the chips are packaged in a more expensive and more difficult to assemble BGA package as compared to the TSSOP package of the previous memory generations such as DDR SDRAM and SDR SDRAM. This packaging change was necessary to maintain signal integrity at higher speeds. For the Bulgarian Go Association, see Bulgarian Go Association. ... A TSSOP (Thin-Shrink Small Outline Package) is a four-sided, rectangular, thin body size surface mount component. ... DDR SDRAM or double-data-rate synchronous dynamic random access memory is a type of memory integrated circuit used in computers. ... SDR memory (front only shown) has 168 pins and two notches. ...


Power savings are achieved primarily due to an improved manufacturing process through die shrinkage, resulting in a drop in operating voltage (1.8 V compared to DDR's 2.5 V). The lower memory clock frequency may also enable power reductions in applications that do not require the highest available speed.


According to JEDEC[1] the maximum recommended voltage is 1.9 volts and should be considered the absolute maximum when memory stability is an issue (such as in servers or other mission critical devices). In addition, JEDEC states that memory modules must withstand up to 2.3 volts before incurring permanent damage (although they may not actually function correctly at that level).


Specification standards

Chips and modules

For use in computers, DDR2 SDRAM is supplied in DIMMs with 240 pins and a single locating notch. DIMMs are identified by their peak transfer capacity (often called bandwidth). Two types of DIMMs: a 168-pin SDRAM module (top) and a 184-pin DDR SDRAM module (bottom). ...

Standard name Memory clock Cycle time I/O Bus clock Data transfers per second Module name Peak transfer rate
DDR2-400 100 MHz 10 ns 200 MHz 400 Million PC2-3200 3200 MB/s
DDR2-533 133 MHz 7.5 ns 266 MHz 533 Million PC2-4200
PC2-43001
4266 MB/s
DDR2-667 166 MHz 6 ns 333 MHz 667 Million PC2-5300
PC2-54001
5333 MB/s
DDR2-800 200 MHz 5 ns 400 MHz 800 Million PC2-6400 6400 MB/s
DDR2-1066 266 MHz 3.75 ns 533 MHz 1066 Million PC2-8500
PC2-86001
8533 MB/s

Note: DDR2-xxx (or DDR-xxx) denotes data transfer rate, and describes raw DDR chips, whereas PC2-xxxx (or PC-xxxx) denotes theoretical bandwidth (though it is often rounded up or down), and is used to describe assembled DIMMs. Bandwidth is calculated by taking transfers per second and multiplying by eight. This is because DDR2 memory modules transfer data on a bus that is 64 data bits wide, and since a byte comprises 8 bits, this equates to 8 bytes of data per transfer. This article is about a unit of data. ...


1 Some manufacturers label their DDR2 sticks as PC2-4300 instead of PC2-4200, and PC2-5400 instead of PC2-5300. At least one manufacturer has reported this reflects successful testing at a faster-than standard speed,[2] whilst others simply use the alternate rounding as the name, as described above.


In addition to bandwidth and capacity variants, modules can

  1. Optionally implement ECC, which is an extra data byte lane used for correcting minor errors and detecting major errors for better reliability. Modules with ECC are identified by an additional ECC in their designation. PC2-4200 ECC is a PC2-4200 module with ECC.
  2. Be "registered", which improves signal integrity (and hence potentially clock speed and physical slot capacity) by electrically buffering the signals at a cost of an extra clock of increased latency. Those modules are identified by an additional R in their designation, whereas non-registered (a.k.a. "unbuffered") RAM may be identified by an additional U in the designation. PC2-4200R is a registered PC2-4200 module, PC2-4200R ECC is the same module but with additional ECC.
  3. Be Fully buffered modules, which are designated by F or FB and do not have the same notch position as other classes. Fully buffered modules cannot be used with motherboards that are made for registered modules, and the different notch position physically prevents their insertion.

Note: registered and unbuffered SDRAM generally cannot be mixed on the same channel. Dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor within an integrated circuit. ... FB-DIMM Architecture Fully Buffered DIMM (or FB-DIMM) is a memory technology which can be used to increase reliability, speed and density of memory systems. ...


Debut

DDR2 was introduced in the second quarter of 2003 at two initial speeds: 200 MHz (referred to as PC2-3200) and 266 MHz (PC2-4200). Both performed worse than the original DDR specification due to higher latency, which made total access times longer. However, the original DDR technology tops out at speeds around 266 MHz (533 MHz effective). Faster DDR chips exist, but JEDEC has stated that they will not be standardized. These modules are mostly manufacturer optimizations of highest-yielding chips, drawing significantly more power than slower-clocked modules, and usually do not offer much, if any, greater real-world performance. 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. ...


DDR2 started to become competitive with the older DDR standard by the end of 2004, as modules with lower latencies became available.[3]


Backwards compatibility

Two PC2-6400 sticks with integrated heat sinks.
Two PC2-6400 sticks with integrated heat sinks.

DDR2 DIMMs are not designed to be backwards compatible with DDR DIMMs. The notch on DDR2 DIMMs is in a different position than DDR DIMMs, and the pin density is slightly higher than DDR DIMMs in desktops. DDR2 is a 240-pin module, DDR is a 184-pin module. Notebooks have 200-pin modules for DDR and DDR2. This article is about the substance or device. ...


Faster DDR2 DIMMs are compatible with slower DDR2 DIMMs; however, the faster module runs at the slower module's speed. Using slower DDR2 memory in a system capable of higher speeds results in the bus running at the speed of the slowest memory in use.


Relation to GDDR memory

The first commercial product to claim using the "DDR2" technology was the NVIDIA GeForce FX 5800 graphics card. However, it is important to note that this GDDR-2 memory used on graphics cards is not DDR2 per se, but rather an early midpoint between DDR and DDR2 technologies. Using "DDR2" to refer to GDDR-2 is a colloquial misnomer. In particular, the performance-enhancing doubling of the I/O clock rate is missing. It had severe overheating issues due to the nominal DDR voltages. ATI has since designed the GDDR technology further into GDDR3, which is more true to the DDR2 specifications, though with several additions suited for graphics cards. The American multinational Nvidia Corporation (NASDAQ: NVDA) (pronounced ) specializes in the manufacture of graphics-processor technologies for workstations, desktop computers, and handheld devices. ... NVIDIA GeForce FX logo The famous Dawn demo was released by NVIDIA to showcase pixel and vertex shaders effects of the GeForce FX Series The GeForce FX (codenamed NV30) is a graphics card in the GeForce line, from the manufacturer NVIDIA. // Overview NVIDIAs GeForce FX series is the fifth... Look up Colloquialism in Wiktionary, the free dictionary. ... Look up Misnomer in Wiktionary, the free dictionary. ... ATI may stand for: ATI Technologies Inc. ... GDDR3 (Graphics Double Data Rate, version 3) is a graphics card-specific memory technology, designed by ATI Technologies. ...


GDDR3 is now commonly used in modern graphics cards and some tablet PCs. However, further confusion has been added to the mix with the appearance of budget and mid-range graphics cards which claim to use "DDR2". These cards actually use standard DDR2 chips designed for use as main system memory. These chips cannot achieve the clock speeds that GDDR3 can but are inexpensive enough to be used as memory on mid-range cards. GDDR3 (Graphics Double Data Rate, version 3) is a graphics card-specific memory technology, designed by ATI Technologies. ...


See also

Look up RAM, Ram, ram in Wiktionary, the free dictionary. ... FB-DIMM Architecture Fully Buffered DIMM (or FB-DIMM) is a memory technology which can be used to increase reliability, speed and density of memory systems. ... SO DIMM is an abbreviation for Small Outline Dual In-line Memory Module, and is a smaller form of DIMM used most often in notebook/portable computers, small form-factor computers (Such as those with a Mini ITX motherboard) and high-end upgradable office printers. ... Dual-channel architecture DDR/DDR2 SDRAM describes a motherboard technology that effectively doubles data throughput from RAM to the memory controller. ... This is a list of device bandwidths: the channel capacity (or, more informally, bandwidth) of some computer devices employing methods of data transport is listed by bit/s, kilobit/s (kbit/s), megabit/s (Mbit/s), or gigabit/s (Gbit/s) as appropriate and also MB/s or megabytes per... This article or section is in need of attention from an expert on the subject. ... In electronic engineering, DDR3 SDRAM or double-data-rate three synchronous dynamic random access memory is a random access memory technology used for high speed storage of the working data of a computer or other digital electronic devices. ...

References

  1. ^ JEDEC JESD 208 (section 5, tables 15 and 16)
  2. ^ Mushkin PC2-5300 vs. Corsair PC2-5400
  3. ^ DDR2 vs. DDR: Revenge Gained

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. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 280th day of the year (281st in leap years) in the Gregorian calendar. ... 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. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 280th day of the year (281st in leap years) in the Gregorian calendar. ...

External links

  • Overview of DDR-II technology
  • Overview of Rambus XDR
  • Overview of QBM
  • DDR2 vs DDR
  • DDR2 low latency vs high bandwidth, Conroe performance

  Results from FactBites:
 
Overclocker Cafe - DDR1 vs. DDR2 - What's it mean to you? (416 words)
DDR2 is the next logical progression for memory standards and speeds.
DDR2 incorporates several new designs and specifications which play a part in it's increased speed.
Voltage requirements for DDR2 are greatly reduced from that of DDR.
DDR2 SDRAM - Wikipedia, the free encyclopedia (1212 words)
DDR2 SDRAM or double-data-rate two synchronous dynamic random access memory is a computer memory technology.
However, both DDR and DDR2 are double pumped; they transfer data on the rising and falling edges of the clock, at points of 0.0 V and 2.5 V (1.8 V for DDR2), achieving an effective rate of 200 MHz (and a theoretical bandwidth of 1.6 GB/s) with the same clock frequency.
The DDR2 prefetch buffer is 4 bits wide, whereas it is 2 bits wide for DDR and 8 bits wide for DDR3.
  More results at FactBites »

 
 

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