Enabling Dual Channel
In order to enable dual-channel architecture, you will need to have:
- Memory controller supporting dual-channel architecture (virtually all current CPUs support dual-channel architecture).
- Two or an even number of memory modules; each pair of modules must be identical.
- Install the memory modules in the correct memory sockets on the motherboard that will enable this architecture.
First, the memory controller must support the dual-channel architecture. As we discussed earlier, current CPUs have this component embedded, so almost all computers nowadays support this technology.
Second, you need to have an even number of memory modules on your system, as each pair of memory modules will be accessed as a single entity. Refer to Figure 4 in the previous page. If you install just one memory module, this technique won’t work because the memory will still be accessed at 64 bits per clock cycle. In other words, dual channel works by accessing two memory modules in parallel, i.e., at the same time. As each pair of memory modules is accessed as a single entity by the memory controller, the modules at each pair must be identical. Each pair, however, can have a different total capacity. For example, you can install two 2 GB modules and two 1 GB modules, for 6 GB total.
This is a very important point to keep in mind when selecting parts for building a PC. Let’s say you want to build a computer with 4 GB of RAM. In order to achieve the best performance, you must buy two 2 GB memory modules to enable dual-channel architecture. If you buy a single 4 GB module, you will have the same memory capacity; however, the memory will be accessed in single-channel mode, with half the bandwidth available.
The third point is to install the memory modules in the correct memory sockets on the motherboard. You have to be very careful; otherwise, you will buy two memory modules as recommended and end up having a system still accessing the memory under single-channel architecture.
In order to make our explanations easier to understand, let’s assume we have a motherboard with four memory sockets and the installation of two memory modules, which is the most common scenario. Number the motherboard memory sockets as one, two, three, and four.
The rules, however, depend on the kind of system you own. Intel, AMD socket AM3+, and a few AMD socket AM3 motherboards follow one rule, while all other AMD-based systems use a different rule. The following explains the differences between the two systems.