Memory Help Pages

2. My motherboard has both spare 72pin SIMM and 168pin DIMM slots. Which should I buy to upgrade my system?

This is actually a difficult question to give a definite answer on that is guaranteed to work. Firstly it is important to consider that SDRam Dimms are noticably quicker than EDO Simms and so all things being equal Dimms would always be preferred. However there are other factors that may affect the answer too.

If your system currently has EDO Simms on it then whether you choose to add simms or dimms then the performance increase is likely to be the same unless you remove the Simms because the system can only use one speed for the ram which of course must therefore run at the rate of the slowest ram.

If your system currently has the Simm slots emply and is running with one or more Dimms then you would tend to want to use Dimms. However, over time the technology of ram chips has changed and older motherboards will not always recognise the newer technology ram. It is for this reason that people with older motherboards sometimes ask for the older PC66 specification Dimm rather than the newer PC100 or PC133 Dimms. Additionally to complicate the matter even further there are cases where certain makes of ram will not run on certain motherboards though they will run faultlessly on others and some motherboards will not accept a mixture of ram specifications. For this reason it is recommended that whenever you buy SDram Dimms you only do so from someone who agrees to take them back if they won't work in your system regardless of whether they are faulty or not. These issues of compatibility are much rarer with EDO Simms and provided you buy 2 at a time (they need to be fitted in pairs) you would expect them to work without problem.