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 It superseded the original DDR SDRAM specification, and is superseded by ..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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However, latency is greatly increased as a trade-off. By using this site, you agree to the Terms of Use and Privacy Policy. 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. From Wikipedia, the free encyclopedia.

These chips are mostly standard DDR chips that have been tested and rated to be capable of operation at higher clock rates by the manufacturer.

DDR2 SDRAM – Wikipedia

Retrieved August 25, This article needs to be updated. An alternative system is found in Amendment 2 to IEC The definitions of kilo, giga, and mega based on powers of two are included only to reflect common usage.

Such chips draw significantly more power than slower-clocked chips, but usually offered little or no improvement in real-world performance.

Views Read Edit View history. This page was last edited on 2 Augustat DDR2 was introduced in the second quarter of at two initial clock rates: The standards specify the physical and electrical characteristics of the modules, and include the data for computer simulations of the memory module operating in a system. By using this site, you agree to the Terms of Use and Privacy Policy. Alternatively, DDR2 memory operating at twice the external data bus clock rate as DDR may provide twice the bandwidth with the same latency.


Retrieved from ” https: The document notes that these prefixes are used in their decimal sense for serial communication data rates measured in bits.

JEDEC JESD79 | DDR SDRAM Specification | Electronics Notes

Dynamic random-access memory DRAM. Retrieved from ” https: 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. This page was last edited on 11 Januaryat The purpose of the standard is to promote the uniform use of symbols, abbreviations, terms, and definitions throughout the semiconductor industry.

Wikipedia articles in need of updating from January All Specfication articles in need of updating. During an access, four bits were read or written to or from a four-bit-deep prefetch queue. DIMMs are identified by their peak transfer capacity often called bandwidth.

The specification notes that these prefixes are included in the document only to reflect common usage.

JEDEC memory standards

The document further refers to the description of the IEC binary prefixes in Amendment 2 of IEC”Letter symbols to be used in electrical technology”for an alternate system of prefixes [notes 1] and includes a table of the IEC prefixes in the note. The specification contains definitions ddt2 the commonly used prefixes kilomegaand giga usually combined with the units byte and bit to designate multiples of the units. Views Read Edit View history.

Thus, DDR2 memory must be operated at twice the data rate to achieve the same latency.

Archived from the original on DDR2 started to become competitive against the older DDR standard by the end ofas modules with lower latencies became available. 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. The two factors combine to produce a total of four data transfers per internal clock cycle.


From Wikipedia, the free encyclopedia. In addition to double pumping the data bus as in DDR SDRAM transferring data on the rising and falling edges specificcation 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.

fdr2 This queue rdr2 or transmitted its data over the data bus in two data bus clock cycles each clock cycle transferred two bits of data. However, further confusion has been added to the mix with the appearance of budget and mid-range graphics cards which claim to use “GDDR2”.

The standards specify memory module label formats for end-user markets. These cards actually use standard DDR2 chips designed for use as main system memory although operating with higher latencies to achieve higher clockrates. At least one manufacturer has reported this reflects successful testing at a higher-than-standard data rate [4] whilst others simply round up for the name.


The lower memory clock frequency may also enable power reductions in applications that do not require the highest available data rates. It had severe overheating issues due to the nominal DDR voltages. 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 the 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.