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 It superseded the original DDR SDRAM specification, and is superseded by ..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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The definitions of specificatioj, giga, and mega based on powers of two are included only to reflect common usage. 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.

DDR2 started to become competitive against the older DDR standard by the end ofas modules with lower latencies became available. 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. Power savings are achieved primarily due to an improved manufacturing process through die specificstion, resulting in a drop in operating voltage 1.

These cards actually use standard DDR2 chips designed for use as main system memory although operating with higher latencies to achieve higher clockrates. In other projects Wikimedia Commons. It had severe overheating issues due to the nominal DDR voltages. DDR2’s bus frequency is boosted by electrical ddd2 improvements, on-die terminationprefetch buffers and off-chip drivers.


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.

The document specifivation that these prefixes are used in their decimal sense for serial communication data rates measured in bits. 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.

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. Retrieved from ” https: Retrieved August 25, 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.

During an access, four bits were read or written to or from a four-bit-deep spwcification queue. Retrieved from ” https: Views Read Edit View history. Views Read Edit View history. The standards specify the physical and electrical characteristics specificatino the modules, and include the data for computer simulations of the memory module operating in a system. 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.

Both performed worse than the original DDR specification due to higher latency, which made total access times longer. The specification defines the two common units of information: Dd2r page was last edited on 11 Januaryat Bandwidth is calculated by taking transfers per second and multiplying by eight. By using this ddr22, you agree to the Terms of Use and Privacy Policy.


The standards specify memory module label formats for end-user markets. Please update this article to reflect recent events or newly available information. 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.

By using this site, you agree to the Terms of Use and Privacy Policy. This packaging change was necessary to maintain signal integrity at higher bus speeds.

JEDEC JESD79 | DDR SDRAM Specification | Electronics Notes

The specification notes that these prefixes are included in the document 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. This article needs to be updated. Dynamic random-access memory DRAM.


An alternative system is found in Amendment 2 to IEC DDR2 was introduced in the second quarter of at two initial clock rates: DIMMs are identified by their peak transfer capacity often called bandwidth. Alternatively, DDR2 memory operating at twice the external data bus clock rate as DDR may provide twice the bandwidth with the same latency.

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. 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.