RAM is one of the best investments you can make in your computer. Not only does it improve system performance; it also holds its value fairly well, in case you ever want to sell it. Unless of course your RAM chips are too 'small' for the needs of a modern pc.

Adding memory is one of the best and cheapest ways to speed up your computer. But there are a number of things you'll want to keep in mind when upgrading your computer with more RAM:

Buy enough RAM for the software you plan to use. With today's computers and operating systems, 256 megabytes of RAM is the minimum for acceptable performance. You'll like your computer even better with 1Gig of RAM. If you're doing intensive graphics work, you may want even more.

Try to buy RAM modules that fill the fewest RAM expansion slots in your computer. That way, if you want to add more RAM later, you won't need to replace the RAM that's already occupying one of the expansion slots.

If you have two empty RAM slots in your computer and want to expand your RAM by 512 megabytes, it makes more sense to plug a 512-megabyte DIMM into one expansion slot than to take up both free slots with two, 256-megabyte DIMMs.

SDRAM speed is measured in megahertz (MHz). Speed markings on the memory chips may still specify nanoseconds, but in this case it represents the number of nanoseconds between clock cycles. To add to the confusion the markings on the chips don't match the Mhz value. RAM modules are measured in megabytes per second. Rambus modules are either 400 or 300Mhz. Because they send two pieces of information every clock cycle, you get 800 or 600Mhz. They have a 16-bit bus width or 2 bytes (16/8). For example, a 400Mhz modules speed is 1600MB a second or 1.6GB a second. (400,000,000 * 2) * 2. The 300Mhz module provides 1.2GBs a second.

The contact material used on RAM modules and expansion sockets should match. That means you should try to match gold pins with gold-plated receptors on an expansion slot, and tin pins with tin receptors.

If speed is what you need, look for EDO (Extended Data Out) RAM, which is about 10 percent faster than regular RAM. But be careful: Adding this type of RAM to motherboards that don't support EDO will cause problems.

Parity RAM is superior to non-parity, and parity RAM with ECC (Error Correcting Code) is best of all. But make sure your motherboard supports parity checking before you spend any extra money on this type of RAM.