What type of computer memory to use in a memory upgrade?

Determining the type of memory required
What to look for in memory
Before purchasing memory
Installing PC computer memory

Determining the type of memory required

Documentation

Computer memory aka RAMBy far the best method of determining the memory (RAM) to use with your computer is through the computer or motherboard manufacturer documentation. If you do not have your product documentation, you can also find it online through the computer manufacturers or motherboard manufacturer website.

For example, your motherboard documentation features may list something similar to the example below.

Supports DDR 400/333/266 SDRAM
Supports up to 3 unbuffered DIMM or 2.5 volt DDR SDRAM
Up to 1GB per DIMM with a maximum memory size up to 3 GB

In the above example, you can see this motherboard supports DDR SDRAM DIMM at speeds of 400, 333, and 266.

Use a third-party tool or service

Another option would be to use a third-party software utility or online service that can provide details about the components in your computer. These utilities can scan your computer and give a detailed report of everything in your computer, including memory. For example, the Crucial System Scanner is a free utility to scan your computer and give you computer memory details including available memory slots.

Visually examine the memory

512MB DIMM example of memory stick

Finally, you can also open the computer being aware of ESD, remove one of the memory sticks currently installed in the computer and physically examine the memory for any stickers or printed labels identifying the memory.

What to look for in memory

Below is a short list of what you should look for or determine when trying to determine the memory your computer has or needs.

Memory type

What type of memory does the computer use? Some examples of the different memory types include DDR-SDRAM, DDR2-SDRAM, DIMM, DRAM, EDO, FPM, SDRAM, LIMM, RDRAM (RAMBUS), RIMM, SIMM, and SODIMM. Today's computers usually use a variant of DIMM/SDRAM memory.

Amount of Pins

How many pins does the computer accept? 72-Pin, 30-Pin, 168-Pin, 184-Pin, or 240-Pin? This all depends on the type of memory.

Speed of memory

Memory may be listed in nanosecond (ns) speeds such as 70ns, 60ns, and 10ns or MHz such as 266MHz, 333MHz, 400MHz, 500MHz, 533MHz, 667MHz, 800MHz. Make sure you get the correct speed of memory for your computer.

Note: If you mix the speeds of your memory in your computer the computer runs at the speed of the lowest speed memory in the computer. Although the computer is still going to work, you are paying more for a higher speed that is not being utilized.

Error-checking

Does the computer require error-checking memory? For example, Parity or Non Parity (ECC or Non-ECC). If you have an option between the two and are uncertain go with memory that has error checking. Typically all memory used with today's computers only use memory with error checking.

Voltage

What are the voltage requirements? Make sure you determine the voltage requirements of the memory (e.g. 1.8v or 2.5v).

Contact material

The contact material on the memory is also important when considering buying computer memory. The contact area is coated in either gold or tin and should match the material of the memory slots. Mismatching the memory and memory slot contact material can cause corrosion.

Proprietary

Finally, is the memory in your computer proprietary, and if it is not, is there a manufacturer that your computer company recommends? If you have a more recent computer (computer made in the last five years) this should not be a concern.

Other terms

See our memory definitions page if there is any other jargon that is confusing you.

Before purchasing memory

Make sure the computer has the available memory slots for the memory you are installing in the computer. For example, if you are installing an additional 1GB of memory into the computer and plan on using two 512MB memory sticks make sure you have two available slots. If you do not have available slots you can remove pre-existing memory and install new memory. However, any memory removed is subtracted from your total. Below is an example of a possible scenario.

Computer memory slots

A computer has 512MB of memory, from four different 128MB sticks of RAM and has no more available slots. If you wanted to upgrade to a total of 1GB of memory each of the 128MB sticks would need to be replaced with either four 256MB sticks or two of the 128MB sticks could be replaced with two 512MB sticks.

Tip: 1GB = 1,024MB

Installing the memory

Additional information