Computer Hardware RAM Information
The terminology surrounding RAM seems to be a dizzying array of bizarre terms. Besides RAM, there is also "SO-DIMM," "DIMM," "DDR," "volatility," and something called "thrashing". It's time to shed some light on these terms.
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RAM
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RAM stands for Random Access Memory. RAM chips store information for programs currently running on the computer.
Volatility
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RAM is volatile. This means that if the computer loses power, then all the information stored in RAM is lost. For this reason, hard drives, CD-ROM drives, or Flash drives are used for permanent storage.
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Virtual Memory and "Thrashing"
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Information in RAM can be accessed by the CPU very quickly, but RAM is usually fairly limited. Virtual memory allows the hard drive to pretend to be RAM, but if this is pushed too far, an unpleasant phenomenon known as thrashing results. A computer that is thrashing can slow down dramatically, perhaps even appear to have frozen entirely.
SO-DIMM versus DIMM
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Consumer RAM is usually divided into two broad types: SO-DIMM and DIMM. The important thing to remember is that the 'S' in SO-DIMM stands for "Small". DIMM chips are larger and are typically used for desktop computers, while SO-DIMM chips are smaller and are generally used for notebooks. There are some exceptions to this rule, however. For example, the Apple iMac desktop computer uses SO-DIMM memory.
DDR
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RAM chips usually have a DDR rating describing its speed. As of 2009, the choices are DDR, DDR2, and DDR3 with DDR being the slowest and DDR3 being the fastest. You will always want to use the highest DDR rating that is compatible with your system. Check out your computer manual for details.
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References
- Photo Credit Image by Flickr.com, courtesy of David Blaikie
