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What's the difference between DDR, DDR2, and DDR3 memory?
Requested and Answered by Gene Amtower [pcbgene] on 20-Apr-2010 15:12 (2235 reads)
These terms represent different memory specifications, most closely related to the electronic interface to the memory module and how other devices exchange information with the memory module. Because memory operations are one of the most critical aspects of computer performance, memory designs are constantly evolving to achieve greater speed and efficiency, directly resulting in overall system performance improvements.

As memory technologies change over time, they are differentiated from each other by unique specification names. DDR memory replaced the older PC100/PC133 specification when it arrived on the scene some years back with a drastic new approach to memory management and associated performance benefits. When the DDR memory technology evolved to the next level, it was different in some respects, most notably the connections on the edge of the memory module (different pin counts and socket lengths). So it was named DDR2 to indicate that it was an improvement over the original DDR specification. DDR3 was the next evolution in memory technology, offering even faster memory operation than both DDR and DDR2 and another change in the physical interface connections.

This difference is important because computer system boards are designed to work with only a single memory specification, so DDR memory will only work in a computer system designed to use DDR memory. The different DDR memory specifications are NOT interchangeable. If you are considering replacing or adding memory modules to your system, you must determine which memory specification works with your system.

When buying memory modules for your computer, in addition to the different memory specifications, memory modules also come in different speed ratings, representing the rate at which the system and memory module can communicate with each other. That's why you see DDR2 memory modules for sale as DDR2-5300 or DDR2-6400. The number after the specification name indicates the speed of the memory module in MHz and is an extremely important consideration when looking at replacement memory modules. Each computer system board supports a range of memory speeds by design, and you must consider the allowable range of memory speeds of your system when selecting memory modules for it. Please note that if your system currently contains a slower speed of memory than its maximum memory speed, you may be able to achieve an immediate performance improvement by replacing the installed memory with the highest speed memory that your system supports. If you are considering this option, your system may operate if you install memory modules of different speeds at the same time, but it can also lead to instability and lockups. To be safe, make sure all memory installed in your system is all the same speed - i.e. to be safe, don't install DDR2-5300 and DDR2-6400 memory modules at the same time.

Finally, you will also see available memory designated as buffered or non-buffered memory. Buffered memory is different than non-buffered memory; most desktop PCs use non-buffered memory while most servers use buffered memory. These two types of memory are also not interchangeable, so be sure to match this aspect of purchased memory to your system.

If you are still struggling to grasp all of these details and you live in the Dayton, OH area, ask PC Backup for help by sending us an inquiry through the Contact Us form on this site or by calling us at (937) 478-7624.

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