DDR2 Memory Definition
Double data rate revision 2 memory, or DDR2, is a class of synchronous dynamic random access memory, or SDRAM. DDR2 memory supersedes the DDR memory specification set forth by the Joint Electronic Devices Engineering Council (JEDEC). DDR2 memory is the current industry standard for computing memory for applications ranging from home desktops to enterprise servers.
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Double Data Rate Explained
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DDR2 uses the same double data rate technology of its predecessor. It can perform memory tasks on both the rising and falling edge of the memory's operating clock frequency. A common analogy is that of a clock cycle and a musical note. Musical notes have both an up and a down beat, just as DDR2 memory can perform data tasks on both the upbeat and downbeat of a clock cycle.
Improvements
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DDR2 memory has been improved over the older DDR memory with the addition of an external data bus to the memory modules. This external data bus allows the DDR2 memory to operate at twice the clock rate of DDR memory, but at twice the latency. Thus, a DDR2 memory module that is set to operate at the same clock frequency as a DDR module will perform the same tasks in twice the time; however, the external data bus of DDR2 memory modules is almost always set to operate at a minimum of twice the clock frequency of the system, and as such will perform twice as fast as DDR memory with the same latency.
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Function
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As with DDR, DDR2 memory is a collection of memory modules that comprise several million integrated circuits. These circuits may read, write or erase data within their cells by storing electrical charges that represent binary data. DDR2 memory uses this process to act as an operating ground for computer programs and their supporting files, as they operate much faster than hard drives and offer better system performance and latencies.
Potential
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Though DDR2 memory is the current standard, there are competing technologies. There is a DDR3 memory specification that is used by the Core i7 Intel processor. Though DDR3 memory does have specific advantages--it has three channels versus a maximum of two for DDR2 memory--and higher transfer speeds and clock frequencies, it is currently only used by this one Intel processor on the market. As more motherboards and processors are introduced that support DDR3 memory, it is almost certain that DDR2 memory will depreciate, much as DDR memory did.
Warning
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DDR2 memory, like all RAM, is a volatile memory type. This means that the data stored within DDR2 memory modules is not persistent. Any interruption of electrical power to the DDR2 memory modules will cause a loss of data. It's important to save often when using a computer for important data processing to avoid data loss due to power failure.
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