The term dual channel refers to a DDR motherboards chipset that’s designed with two memory channels instead of one.The two channels handle memory-processing more efficiently by utilizing the theoretical bandwidth of the two modules, thus reducing system latency, the timing delays that inherently occur with one memory module. For example, one controller reads and writes data while the second controller prepares for the next access, hence, eliminating the reset and setup delays that occur before one memory module can begin the read/write process all over again.
Think of this as parallel processing of data with 2 different resources. Lets take and example to make it understand more clearly.
In this above image what we see is 2 dims operating as single channel. here this will increase the size of memory but not the bandwidth. Think in this way, suppose you have installed 2X4 GB sticks in single channel. If you now give then 8 GB of data to process, it will be processed in a linear manner as as both of them resides on same bandwidth.
Now check this image. Here we are using same sticks in dual channel.
If you see now the memory is 4GB but the bandwidth is doubled. In the real time if you check your system configuration in “My computers” it will not show you 8 GB but little less than that. “Then why is this useful?” you probably are thinking the same like I did. So the answer to this question is now the system has two different platform to communicate with the ram. If 8 GB data has to be processed it can be distributed in both the channels evenly and you get similar ram capacity. But the main usage of this architecture is you can actually use two modules to work simultaneously. For eg, if 1 dimm is processing some data other can be utilized to render images. which is not possible in single channel approach.
Coming to this multi channel architecture, other than dual channel we also have triple and quad channel motherboards available. We can expect them to be even faster.
If you want to purchase a RAM that has to work for dual, triple or quad channel you should look out for that kit. For eg a dual channel kit will have 2 dimms that will have similar timings which is very important. If you mix and match then it is possible you may end up bringing down the total frequency and memory to a single ram stick. So if you want 8 GB in dual channel do not go for 2+4+2 utilizing 3 ram slots on the other hand you should utilize similar color coded ram slots in 2+2+2+2 format or 4+4 format with similar sticks (in timing and size, brand is also preferred).