Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I am curious about what to look for when purchasing RAM in terms of what specifications to pay attention to. I know that the RAM has to be the same standard (DDR, DDR2, DDR3, etc) and I know that if you get RAM of different speeds they will operate at the speed of the slowest RAM, but are there any other factors to consider? Does the voltage, cas latency, or timing of the RAM matter, or will mixing RAM with different voltages, cas latency, and/or timing cause damage to the computer or motherboard?

Thank you for your answers.

share|improve this question

Voltage, Latency and timings are not important factors.

... Well, Voltage is very important - but if you get standard grade desktop commercial components, they should all meet the standard. It is just some overclocked or special server memory uses different voltage, however they are usually more expensive and warn you.

Latency and timings, there are rare instances where it is not possible to have differences - usually some chipsets/motherboards prevent this, however, in most instances you will just get a warning when you start the machine and it will operate at a low speed (or even a penalty speed where it is slightly lower than the lowest - only seen this once on a American Megatrends BIOS years ago).

As it is part of your question - it shouldn't cause any damage to the machine. The machine is designed for the memory socket. At worst you will get a beep warning and/or the memory will run slow. I cannot imagine any irreversible damage. Even if you had memory requesting higher voltage, I could imagine the memory stick failing before the motherboard - but don't test it or quote me on that!

As for buying, my guide will always be to try and buy a matching / identical second stick as this enables dual (or higher) channel memory support, if your motherboard supports it. This mode can (under some circumstances) dramatically increase memory performance.

share|improve this answer

Take a look this reference

DDR SDRAM Standard  Frequency (MHz)     Voltage[10]
- DDR                    100–200           2.5/2.6
- DDR2                  200–533             1.8
- DDR3                  400–800             1.5

DDR (DDR1) has been superseded by DDR2 SDRAM, which has some modifications to allow higher clock frequency, but operates on the same principle as DDR. Competing with DDR2 are Rambus XDR DRAM. DDR3 SDRAM is a new standard that offers even higher performance and new features.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.