January JEDEC. STANDARD. DDR2 SDRAM SPECIFICATION be addressed to JEDEC Solid State Technology Association, Wilson Boulevard. DDR2 SDRAM is a double data rate synchronous dynamic random-access memory interface. It superseded the original DDR SDRAM specification, and is superseded by .. JEDEC standard: DDR2 SDRAM Specification: JESDF, November ** ยท JEDEC. The JEDEC memory standards are the specifications for semiconductor memory circuits and Memory modules of the DDR2-SDRAM type are available for laptop, desktop, and server computers in a wide selection of capacities and access.

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Retrieved from ” https: Dynamic random-access memory DRAM.

The specification defines the two common units of information: The two factors combine to produce a total of four data transfers per internal clock cycle. Please update this article to reflect recent events or newly available information.

The specification contains definitions of the commonly used prefixes kilomegaand giga usually combined with the units byte and bit to designate multiples of the units. However, further confusion has been added to the mix with the appearance of budget and mid-range graphics cards which claim to use “GDDR2”.

This committee consists of members from manufacturers of microprocessors, memory ICs, memory modules, and other components, as well as component integrators, such as video card and personal computer makers.


DDR2’s bus frequency is boosted by electrical interface improvements, on-die terminationprefetch buffers and off-chip drivers. The purpose of the standard is to promote the uniform use of symbols, abbreviations, terms, and definitions throughout the semiconductor industry.


DIMMs are identified by their peak transfer capacity often called bandwidth. Views Read Edit View history. Thus, DDR2 memory must be operated at twice the data rate to achieve the same latency.

This article needs to be updated.

By using this site, you agree to the Terms of Use and Privacy Policy. The lower memory clock frequency may also enable power reductions in applications that do not require the highest available data rates. DDR2 was introduced in the second quarter of at two initial clock rates: In addition to double pumping the data bus as in DDR SDRAM transferring data on the rising and falling edges of the bus clock signalDDR2 allows higher bus speed and requires lower power by running the internal clock at half the speed of the data bus.

Archived from the original on From Wikipedia, the free encyclopedia. During an access, four bits were read or written to or from a four-bit-deep prefetch queue. The definitions of kilo, giga, and mega based on powers of two are included only to reflect common usage. This packaging change was necessary to maintain signal integrity at higher bus speeds.

Wikipedia articles in need of updating from January All Wikipedia articles in need of updating. In other projects Wikimedia Commons. From Wikipedia, the free encyclopedia.

Retrieved from ” https: This page was last edited on 2 Augustat The standards specify memory module label formats for end-user markets. At least one manufacturer has reported this reflects successful testing at jedce higher-than-standard data rate [4] whilst others simply round up for the name. JEDEC standards and publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting speccification purchaser in selecting and obtaining with minimum delay the proper product for use by those other than JEDEC members, whether the standard is to be used either domestically or internationally.



The document notes that these prefixes are used in their decimal specificatkon for serial communication data rates measured in bits. Views Read Edit View history. However, latency is greatly increased as a trade-off. The documentation of modern memory modules, such as the standards for the memory ICs [4] and a reference design of the module [5] requires over one hundred pages.


It had severe overheating issues due to the nominal DDR voltages. An alternative system is found in Amendment 2 to IEC This queue received or transmitted its data over the data bus in two data bus clock cycles each clock cycle transferred two bits of data. These cards actually use standard DDR2 chips designed for use as main system memory although operating with s;ecification latencies to achieve higher clockrates.

Such chips draw significantly more power than slower-clocked chips, but usually offered little or no improvement in real-world performance. By using this site, you agree to the Terms of Use and Privacy Policy. DDR2 started to become competitive against the older DDR standard by the end ofas modules with lower latencies became available.