Overview

Random Access Memory (RAM) provides space for your computer to read and write data to be accessed by the CPU (central processing unit). When people refer to a computer’s memory, they usually mean its RAM.

If you add more RAM to your computer, you reduce the number of times your CPU must read data from your hard disk. This usually allows your computer to work considerably faster, as RAM is many times faster than a hard disk.

RAM is volatile, so data stored in RAM stays there only as long as your computer is running. As soon as you turn the computer off, the data stored in RAM disappears.

When you turn your computer on again, your computer’s boot firmware (called BIOS on a PC) uses instructions stored semi-permanently in ROM chips to read your operating system and related files from the disk and load them back into RAM.

SDR, DDR, DDR2, and DDR3 RAM

Several types of RAM are used in modern computers. Before 2002, most computers used single data rate (SDR) RAM. Most computers made since then use either double data rate (DDR), DDR2, or DDR3 RAM. DDR2 is able to achieve faster transfer rates to prevent limitation of your CPU’s performance, and DDR3 technology takes these advancements even further.

Note that these RAM technologies are not interchangeable. One type of RAM will not function if installed with another type, and physical differences in the RAM modules prevent them from even being inserted in the same computer.

Caveats

• It is best to buy from an established and reputable seller. Check their reputation through Google, or resellerratings.com Store Ratings

• Check the type of RAM you need before ordering. Best is to buy from a seller who offers a compatibility list or an online configurator that identifies the correct RAM part number for your Mac or PC.

• eBay and other auctions are a risky place to buy RAM. Besides the normal risks of outright scams and frauds like used instead of new, non-functioning, or not as described items, there is a % of counterfeit RAM on the market, especially in flash memory cards for cameras and phones. It has been estimated that 90% of the SanDisk flash memory on eBay are forgeries. RAM that has been pulled from machines (such as the RAM that comes out of an Apple when you upgrade) has no warranty. Getting refund / repair / warranty service from an eBay vendor is considerably riskier than from an established vendor with a physical location.

• International purchases: When purchasing from outside your country, while the seller may advertise “no taxes or extra charges” you are almost certainly going to be charged for some or all of: VAT/GST/local tax, duties, customs brokerage fees, and/or advancement fees when the package arrives in your country. UPS Ground courier is notorious for charging low shipping costs but sky-high brokerage costs. These fees can substantially increase the cost of your purchase. Air freight is expensive, but often includes the customs brokerage, so it may be a wash against the cost of ground + brokerage. The least expansive way to import goods is through normal postal parcel mail. Unfortunately, that is also the method that is most prone to loss or theft. Always insist on a shipping method that includes insurance and a tracking number.

• In addition, if there is any warranty issue with your internationally purchased RAM, you can expect to pay shipping costs and customs clearing costs both ways, which can be expensive.

Warranties

It is always recommended that where ever you purchase RAM from, you check their warranty and returns policies. Many cheaper suppliers only give you a 1 year warranty and will not accept returned RAM unless it’s faulty. RAM, after being removed and reinserted a number of times, may have the connections wear down. Thus the lifetime warranty, or a 5-year warranty, may come in handy. Apple only allows 1 years with their RAM. Check to see whether warranty is handled by the seller, or whether they force you to deal with the manufacturer for warranty replacement (this is a problem with manufacturers like Samsung who do not sell retail and will refuse to deal with you as an end user).

Will it make my machine faster?

Taking your foot off the brake does not make your car go faster – it just discontinues slowing it down. Less reading and writing back and forth to your slow hard drive.

Increasing the memory in the Mac or PC does not increase the Machines’s speed — rather it removes slowdowns that result from your programs and data not having enough memory. When there isn’t enough memory for all you are doing, OS is forced to swap memory space on and off the hard drive. Because hard drives are much slower than RAM, this slows the machine down overall.

How much your machine slows down depends on how you are using it. If you use just one program at a time, and don’t open large data sets, then you may not notice a speed difference with more RAM. If you regularly multitask many programs, or use ‘hungry’ programs (like Photoshop, virtualization (Parallels, VMWare), digital video or digital audio software), then you should see noticeable improvement with 3 GB or 4 GB RAM.

When you are running multiple programs at once, more RAM makes switching from one program to another faster, because many OS can cache the previous program’s memory in ‘inactive’ memory for a longer time before it has to get flushed out to make room.

Which RAM to Buy

First step is to order from a reputable dealer who guarantees compatibility with your model Mac or PC, so you don’t have to know which specific modules to order.

You can also look up the correct modules at the better vendors’ websites, which have configurators such as Data Memory Systems, Kingston and Crucial (one thing, Crucial sometimes recommends premium RAM that is faster than the particular Mac can take advantage of. It will work, but the extra expense is wasted)

Notes: In some cases older machines are ‘officially’ specified for slower modules, but compatible faster modules are commonly substituted – PC2700 for PC2100, or PC133 for PC100. The more common permissible faster modules are quoted below. Also note that “PC133″ or “PC2700″ is not a complete description of a memory module, and there are multiple other factors that determine compatibility. For example you can’t assume that every PC133 memory module will work in a Mac that takes PC133.

Source: macrumors

About the author:  I'm a professional software engineer, a system analyst and userbility expert. I do professional training on several IT related subjects also provide consultation. I am a founder of Qusaz intelligent solution company. I love to blog from time to time, whenever I find some interesting topic that might help others. Read more from this author