As computers have changed drastically over the years, so too have their supplies of memory grown and adapted. Random access memory, or RAM as we know it today, has been in use since a little company named Intel invented the semiconductor chip in 1968. The ones still used today make up a much short list, starting in the 1990s with the single in-line memory module, or SIMM.
Before discerning more specific things, like how much memory the RAM module contains or what speed it is, it is best to determine the type. The first step to doing this is to count the number of pins on the bottom of the RAM chip.
The newest SIMM chips, which are more than 10 years old, usually have 72 pins, but earlier models had only 30. The pins, or contacts, will only be present on one side of the chip. SIMMs are rarely used in computers anymore.
SIMMs eventually were replaced by DIMMs, which have contacts on both sides of the RAM chip. DIMMs are the most common types of RAM, covering a wide spectrum of dynamic RAM, or DRAM. A general rule of thumb is that the more pins the RAM contains, the newer it is. DIMMs can come with numbers of pins ranging from 168 to 240. Chips with 168 pins means it's a single data rate chip, 184 pins means it's a double data rate chip, and 240 pins indicates a DDR2 or DDR3 chip.
Some DIMMs don't fall in line with the rest. Although most desktop DIMMs are just over 5 inches long, small outline DIMMs, commonly used in laptops, are only between 2 and 3 inches long. The number of pins ranges from 144 to 204, with 144 being SDR, 200 being DDR or DDR2, and 204 being DDR3.
Aside from identifying the type, it is useful to know the amount of memory and clock speed of the RAM. This can be accomplished, more often than not, by a sticker or other label on the outer surface of the RAM chip. If the information on the sticker or label isn't clear enough, you can go to the manufacturer's website and enter the chip's part number, both of which should be located on the chip. This will tell you the amount of memory on the chip and at what speed it operates. If the chip is missing a label, it will need to be plugged into a corresponding computer to check its information.
If the RAM fits a handy computer's motherboard, plug it in and see if it boots. Remember, the number of pins and location of pins will need to match. Don't force it. Afterward, find a good program, such as memtest86+, to test the RAM and find out its specifications.
- Photo Credit ram 2 image by PeteG from Fotolia.com
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