How Dual Channel DDR works
Dual Channel DDR works by giving the north bridge two independent controllers to access two sets of memory. To put things in simpler terms, think of a stick of DDR as a two way bridge. DDR achieves double the data rate of normal SDR memory by allowing an independent data path for upstream and downstream travel; much like how a bridge or road works. The theoretical maximum amount of bandwidth for a stick of DDR400 is 3.2GB per second. Like a bridge with a speed limit, the amount of throughput achieved varies depending on the type of data it deals with.
With Dual Channel DDR, the data path is doubled once again by using two sticks of DDR memory.
By giving the CPU/north bridge another data path to the memory, bandwidth is effectively doubled, giving Dual Channel DDR400 6.4GB/s. In simple terms, think of DCDDR as widening the bridge by adding two more lanes. This effectively allows more data to travel faster; much like traffic moving faster when there’re more lanes to drive in. The downside to this is traditional DCDDR solutions require pairs of same sizes.
In more technical terms, DDR memory is 64bit and communicates with the CPU/north bridge at 64bit.
Dual Channel DDR can operate in two modes. One mode is it accesses the memory in 128bit mode, which is how most DCDDR chipsets operate. The other mode is it communicates with the two memory controllers in 2x64bit mode, treating each controller individually.
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