How to Buy Memory for a Computer: 5 Steps - MakeSureHow
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There are many different kinds of computer memory and it can be confusing to know the right kind to select. When you're buying memory for a computer, first determine how much memory you need and how much your computer will support. Then shop for memory that matches the type and speed required by your computer or motherboard. You can generally purchase brand-name and generic-brand memory from local and online retailers. It's best to buy memory in pairs and ideal if all your computer memory is of an identical brand and model.


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    Amount of Memory: The amount of memory you need in your computer depends on your motherboard, operating system and how you use the computer. Your motherboard determines the maximum amount of memory you can install. However, if you use a 32-bit operating system, your computer will only recognize about 3 GB, regardless of how much you install. If you multitask, play games, edit photos or videos or use professional applications such as Microsoft PowerPoint, you'll get the best performance from your computer by having 3 GB of memory with a 32-bit operating system and 4 GB or more with a 64-bit operating system.
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    Memory Modules: Computer memory, also called SDRAM, comes on a printed circuit board with connecting pins that fit the motherboard's memory slot. There are two types of circuit boards: Dual In-line Memory Module (DIMM) and Small Outline DIMM (SODIMM). DIMMs, used in most desktops, are long and rectangular. SODIMMs, used in most laptops and in the Intel-based Mac, are more square. You don't need to consider the number of pins on the circuit board when buying memory because it's a fixed standard based on the size and type of memory: DIMMs have 184 pins for DDR and 240 pins for DDR2 and DDR3; SODIMMs have 200 pins for DDR and DDR2 and 204 pins for DDR3.
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    Memory Type and Speed: Most SDRAM is Double Data Rate (DDR) memory, which comes as DDR, DDR2 and DDR3. All three memory types have both DIMM and SODIMM versions. Each type of DDR memory also has multiple speeds; for example, DDR ranges from DDR PC2-2700 to DDR PC2-8500, with a higher number indicating faster memory. When buying memory, first determine if you need DIMM or SODIMM; then determine if you need DDR, DDR2 or DDR3; then determine the highest speed your computer supports. There is an online tool (see link in Resources) that can help you ientify the exact type of memory you need.
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    Memory Retailers: You can buy memory at retail stores and from online retailers. Many online retailers also sell generic brands of memory that are usually less expensive than recognized manufacturers. However, you should carefully review the return or exchange policy of the site from which you buy the memory and compare the warranty of the generic memory to the warranty provided by a recognized manufacturer. The safest option is to purchase a recognized brand of memory from a reputable retailer such as RadioShack, in case you have problems.
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    Memory Pairs: If you have four slots for memory in your motherboard, it's best if all four memory modules are identical. At a minimum, each pair of memory should match. If one module goes bad and you can't buy the exact same brand and model, buy two modules and replace the pair. If you use dual-channel memory, you'll only use one channel if the memory pairs aren't identical. If you have four memory slots, memory pairs are installed in opposite slots, not right next to each other. Review the documentation for how to properly replace memory before you install an upgrade.

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