RAM module compatibility

Helpline Q&A Directory

I have installed two RAM modules in my PC - one of 128MB and the other 256MB - and both run at the same speed: 133MHz. Is that okay, or would it be better if the two modules had the same amount of RAM?

This is okay. In fact, it's pretty common for people to upgrade the RAM in their computers by adding a different size of module from the one already there. It's usually important for the modules to be of the same speed and type, though.

Bear in mind, however, that replacing two memory modules with a single module can actually slow many systems down, as the memory controller is unable to 'interleave' accesses to consecutive memory locations by reading or writing to both modules at the same time.

Some motherboards have restrictions on the types of modules that can be placed in certain slots, so it's advisable to check the manual before buying. If in doubt, specify the make and model of your PC (or motherboard) when ordering the RAM. This places the responsibility on the supplier to provide you with the correct type of memory for your PC.

When installing memory, be aware that memory modules can be damaged by handling unless antistatic precautions are taken. Before installing memory you should buy a wriststrap, which will discharge static build-up safely to the computer case while you do the job.

If this seems like overkill just to perform one memory upgrade, earth yourself by touching an earthed metal object, such as a radiator, before handling electronic parts. Hold memory modules by the upper corners: never touch the electrical contacts or the memory chips.