A Computers RAM (Random Access Memory) is the place in a computer where the operating system, application programs, and data in current use are kept so that they can be quickly reached by the computer's processor. RAM is much faster to read from and write to than the other kinds of storage in a computer, the hard disk, floppy disk, and CD-ROM. However, the data in RAM stays there only as long as your computer is running. When you turn the computer off, RAM loses its data. When you turn your computer on again, your operating system and other files are once again loaded into RAM, usually from your hard disk.

RAM can be compared to a person's short-term memory and the hard disk to the long-term memory. The short-term memory focuses on work at hand, but can only keep so many facts in view at one time. If short-term memory fills up, your brain sometimes is able to refresh it from facts stored in long-term memory. A computer also works this way. If RAM fills up, the processor needs to continually go to the hard disk to overlay old data in RAM with new, slowing down the computer's operation. The bottom line is that adding memory makes your computer more efficient and allows you to do more things at once.

Our Buyer's Guide will help to make you a savvier consumer and help you navigate the through the wide array of Computer RAM available today.

We will guide you step by step through important aspects of choosing the RAM most suitable for your needs

Step one: Determine how much memory you really require

Below are two guidelines, one based on applications used and another based on the operating system, which will help you determine about how much RAM you will need.

Application based:

Operating System Based: (Minimum Requirements)

Step 2: Determine how much and what type of RAM you already have installed.

If you are not sure how much RAM you currently have on board, the easiest way to figure this out is to go to the Start menu, click Settings, and then click Control Panel. Click System and then select the General tab. At the bottom of the page you should see the amount of RAM.

Determine what type of RAM you need: Before you purchase memory, you need to know what kind to get. To determine the maximum amount of RAM your computer can handle as well as the speed, consult your computers owner's manual, which should show you the number of slots (the place where you insert the RAM), how much each can take, and the maximum your system can use.

To find out what kind of module you will need, you can also open up your computer and get the make and model of the mother board with that information in hand, the motherboard vendor should be able to tell you what type and how much RAM you can install.

Step 3 Choosing features

When it comes to choosing RAM there are a few key features that you will need to be aware of

Speed

Sometimes expressed in MHz, but often as a "PCnnn" number where nnn can be a number like 100, 133, 2700, 3200, 4200, 5300, or many others. Hereis a speed equivalency table:

• PC2700 is the same as DDR-333 MHz
• PC3200 is the same as DDR-400 MHz
• PC2-4300 is the same as DDR2-533 MHz
• PC2-5300 and PC2-5400 are the same as DDR2-667 MHz

Memory Type

Here you'll see any number of acronyms, including SDRAM, DDR, DDR2, FB-DIMM, and more. You cannot substitute one type for another -- DDR2 is not backwards compatible with DDR for example. There's also ECC (error correcting RAM). Really old systems may even have FPM or EDO RAM. Below is a breakdown of speeds that each type of RAM is capable of:

• SDRAM - SDRAM comes in three speeds; 66MHz, 100Mhz and 133Mhz.
• DDR RAM - DDR has a larger range of speeds than SDRAM and comes in 266Mhz (also known as PC2100), 333Mhz (PC2700), 400Mhz (PC3200) and 533Mhz (PC4000).
• DDR2 and 3 RAM - DDR2 and 3 is the second generation of DDR and is faster than its predecessor.

Format

DIMM (desktop full sized modules), SO-DIMM ('notebook' size modules)

Number of Pins

Different physical sizes of memory chips usually have different numbers of pins. Common numbers for current machines are 184 pins, 200 pins and 240 pins.

CAS Latency

This one isn't quite as important; the right type and speed of memory should work even if the CAS number is slower. Adding memory with faster CAS than your machine supports won't speed anything up, and adding memory with a slower CAS will probably only be a small percentage slower.

Dual Channel

Many computers use dual channel memory. In a few cases, this means that memory must be installed in matched pairs. Your computer's manual would say so if that's true. For the majority of cases, unpaired chips will work fine, but matched pairs will result in a slight speed increase (on the order of a few percent).

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. 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).

Summary

With price points continually coming down and feature sets continually going up, it is a great time to purchase RAM for your computer. With all of the above considerations in hand you should now be better equipped to make a more informed choice when choosing computer RAM that is both compatible with your system and best suits your needs.