What size module should I buy?

As long as you don't exceed the maximum memory for your system, bigger is better. We recommend buying the largest module (highest number of MB) that fits into your budget.

To make sure you don't exceed the maximum memory for your system, subtract the amount of memory currently in your system from the maximum memory listed in your system specifications. For example, if your system can take a maximum of 512MB RAM, and you currently have 256MB installed, you can install up to 256MB of additional RAM (512MB - 256MB = 256MB)

Which speed and memory technology should I buy?
In general, you should match the speed and type of memory technology that is already in your system. If you don't know exactly what type of memory you currently have, don't worry; any of the modules listed in the Memory Selector™ for your system should work fine.

Common types of memory technology include fast page mode (FPM), extended data out (EDO), synchronous dynamic random access memory (SDRAM), and double data rate SDRAM (DDR or DDR SDRAM). Most systems will accept only one type of memory technology. (The very few motherboards that can accept more than one type of memory will only allow you to use one type at a time.)

Memory speeds are written in different formats depending on the type of memory technology your computer uses. FPM and EDO speeds are written in nanoseconds (ns). SDRAM and DDR speeds are written in megahertz (MHz) or with a "PC" rating.

It may seem confusing, but faster memory will NOT necessarily make your system faster. Your computer will only run as fast as the "slowest link" in your system, so you can't speed up your computer by adding faster memory. The way to make your system faster is to add more megabytes (MB) of memory.

Here's a rough guide to relative memory speeds. Remember, it's best to match the memory that is currently in your system.

Do I need error checking?
When choosing among ECC, parity, and non-parity memory, you need to match what is already in your system. You can tell which kind you have by looking at one of the modules currently in your system. Count the number of black chips on one module. If the number of chips can be evenly divided by three or five, you should buy ECC or parity (whichever is offered for your system). If not, you should buy non-parity.

For example, if one of your modules has nine chips, you should buy ECC or parity. If one of your modules has eight chips, you should buy non-parity.

If you're building your own system, we recommend using non-parity parts unless you will be using your system as a server or have a need for error checking. ECC and parity parts are slower than non-parity parts.

What does "CL" stand for?
CL stands for "CAS latency," which is the number of clock cycles it takes before data starts to flow once a command is received. Low CAS latency is faster than high CAS latency. However, faster memory will NOT necessarily make your system faster. Your computer will only run as fast as the "slowest link" in your system, so you can't speed up your computer by adding memory that is faster than your current memory. The way to make your system faster is to add more megabytes (MB) of memory.

If you're building your own system, we recommend using parts with low CAS latency.