Dual Channel
From TPU Reference
Dual Channel is a technology to improve the maximum bandwidth of a memory bus. It is available for DDR and all subsequent memory standards.
In today's computer systems the CPU is several orders of magnitude faster than the memory. This creates a bottleneck because in some cases the CPU can request/send out data faster than the memory system can handle it, which limits the total system performance.
A single DDR (and DDR 2) memory module has a data width of 64 bits. This means that in one operation you can write 64 bits of data (8 bytes). In Dual Channel mode the data transfer width is doubled to 128 bits by logically "joining" two modules together to form a wider data bus. This requires that both modules are of the same size, running the same (or very similar) timings. Ideally, the two modules are identical make and model.
Installation of memory modules to enable Dual Channel depends on the motherboard. Memory has to be installed in pairs. Often the combinations are indicated by slots of the same color. There is no common system whether to use adjacent slots or one empty slot between modules for Dual Channel. Most manufacturers are using one empty slot between the Dual Channel modules, because this allows better cooling of the individual modules. The POST screen often indicates the active memory configuration, look for "128 bit" or "Dual Channel" as opposed to "64 bit" or "Single Channel". Another way is to check using CPU-Z.
