Almost all new PCs allow the RAM memory to work under a scheme called “dual channel”. Under this scheme the memory transfer rate is doubled (at least theoretically), as the processor (in the case of AMD64 CPUs) or the north bridge chip (in the case of all other CPUs) will access the memory at a 128-bit rate, instead of 64-bit. Nowadays all new PCs accept this feature, except the ones based on socket 754 CPUs from AMD (e.g., Sempron).
So you need to check whether this feature is enabled or not on your PC in order to make it to achieve a higher performance.
To use this feature you need to use two or an even number of memory modules, i.e., if you have just one memory module, dual channel won’t be enabled. Thus it is better to have two 256 MB memory modules than a single 512 MB to make your 512 MB RAM, for example.
Also, it is not just a matter of having two modules installed; they must be installed in the correct sockets. This is really tricky because it depends on the motherboard. Some motherboards require that you install the modules sequentially (i.e., the first module on the first socket and the second module on the second socket), but the majority of motherboards require you to jump one socket (i.e., the first module on the first socket and the second module on the third socket). Many manufacturers use colored sockets in order to differentiate the memory sockets, but also there is no fixed rule here. Some motherboards require you to install the two modules on sockets with the same color; others require you to install the two modules on sockets with different colors. So there is no fixed rule here and you should check the correct installation by reading your motherboard manual.
There are two basic ways to check whether your PC is using dual channel or not. The first one is by checking what appears on the screen right after you turn on your PC. The second way is by running a hardware identification program. If your PC isn’t using dual channel, you will need to check what is going on: or you have just one memory module installed (and should replace it with two modules or buy another identical module and install it on the motherboard) or the two memory modules you have are wrongly installed (i.e., the second module is installed on the wrong socket).
On Figures 12 and 13 you can see what should appear on the screen right after you turn on your PC. If your PC memory is configured under single channel, “single channel”or “64-bit mode” should appear; otherwise “dual channel” or “128-bit mode” should be shown – what we want.
Pay attention that many motherboards are nowadays showing a big colored screen with the motherboard manufacturer logo instead of this text screen; you should hit TAB during this graphical screen in order to switch to this text-mode screen. Also, this screen is shown only for just one or two seconds, so you may need to hit the Pause key in order to read what is written there.
As we mentioned, another way for checking your memory configuration is by running a hardware identification utility. We recommend Hwinfo. Install and run this program and you should see the memory configuration by clicking on “Memory” on the left tree menu. On Figures 14 and 15 you can see our PC configured under single channel and dual channel, respectively (check the “Memory runs at” line).
As we mentioned, if your memory is configured as single channel you should check what is wrong.