Enabling Dual Channel

In order to enable dual channel technology you need to have:

• Compatible chipset and motherboard (Intel CPU) or compatible CPU (AMD).
• Two or four identical memory modules, compatible with the technology supported by the motherboard (DDR-SDRAM, DDR2-SDRAM or DDR3-SDRAM).

AMD CPUs based on sockets 939, 940, AM2, AM2+ and F (1207) are compatible with dual channel technology (socket 462 motherboards with nForce 2 chipset are also compatible). For the Intel platform you will have to check on the motherboard manual or specs page on the manufacturer’s website to see if the motherboard is compatible with dual channel technology.

If you have only one memory module dual channel isn’t available. So if you want a PC with 2 GB of RAM the best way to achieve this is by using two 1 GB modules instead of one single 2 GB module, because on the first case you can enable dual channel mode (which increases performance), while on the second you can’t.

If your motherboard has only two memory sockets – which is more common to happen with entry-level motherboards – then to enable dual channel you have to simply install two memory modules.

On motherboards with four memory sockets, which is the most common scenario, the correct way to enable dual channel technology varies.

If you have four memory modules simply install all of them and dual channel method will be enabled.

If you have two memory modules – which is the most common situation – you have to pay attention.

In order to facilitate our explanations, let’s number the motherboard memory sockets as 1, 2, 3 and 4.

Motherboards Targeted to Intel CPUs

On motherboards targeted to Intel processors, usually dual channel is enabled by skipping one memory socket. So you have to install your first memory module on socket 1 and the second memory module on socket 3, skipping (leaving empty) socket 2. Installing the first memory module on socket 2 and the second memory module on socket 4 will also work.

To make dual channel installation an easier process most of the manufacturers use the same color for sockets 1 and 3 and a different color on sockets 2 and 4, see Figure 4. So in order to enable dual channel simply install your memory modules on sockets with the same color (it doesn’t matter which color you pick).

ATTENTION: the only manufacturer that doesn’t follow this scheme is MSI; on most motherboards from this manufacturer sockets 1 and 2 use the same color while sockets 3 and 4 use another color, see Figure 6. The problem is that some of their products follow the scheme explained on the above paragraph! So on motherboards from MSI don’t follow any color code: use the skipping method (i.e. leave one empty socket between the two memory modules, see Figure 5).

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Figure 4: Memory socket arrangement on a typical socket 775 (Intel) motherboard.

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Figure 5: Memory modules correctly installed in dual channel mode (see the empty socket between them).

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Figure 6: MSI uses a different color scheme.

Here is a more technical explanation: sockets 1 and 2 are physically connected to channel “A” while sockets 3 and 4 are physically connected to channel “B”. When you install memory modules on sockets 1 and 3 or 2 and 4, you are installing each memory module on a different channel, thus enabling the 128-bit access mode. If you install memory modules on the same channel (by installing them on sockets 1 and 2 or 3 and 4) the memory controller will only see a 64-bit device and thus dual-channel mode won’t be enabled.

Enabling dual-channel on systems based on AMD CPUs is a little bit different. Let’s see how it is done.

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