Parallel memory, also frequently referred as "dual-channel memory," permits a PC to access two memory modules concurrently, in parallel, in theory doubling the speed at which a PC can access information stored in memory. Parallel memory, though, is a motherboard aspect, not a particular type of memory. All memory can be accessed through dual channels if motherboard is so ready and PC is organized properly.
To test for dual-channel memory, initially you should check motherboard. The information’s below are for desktop PCs only. Check user's manual if you have a laptop computer.

Instructions

Examining your motherboard

1. Step 1

Switch off and unplug PC. Put it in an unmated, static-free environment like on a dining table or kitchen.

2. Step 2

Open PC and look for memory modules. These are tiny cards, about 1/2" x 2” that are put into slots on motherboard. They usually have a row of flat blocks (chips) on every side of card.

3. Step 3

You will contain 1-4 memory modules and 1-4 memory slots. Look at a slot where existing memory is installed, then look for same slots next to it. If you have less than four memory slots, motherboard possibly does not support dual-channel memory.

4. Step 4

If you have four memory slots, see how they are organized and whether any of the slots are color coded. If two slots are marked with a certain color and other two with a new color, then motherboard possibly supports dual-channel memory.

5. Step 5

For dual-channel memory to be utilized, both paired slots should be busy by matching memory. If you have two memory modules, one in a slot of a colored pair and other in a slot of other colored pair, then PC is not using dual-channel memory. If two memory modules share paired slots, then PC is probable using this aspect.

6. Step 6

Memory in corresponding slots must be matched depending on ability, speed and number of chips and sides. Many companies sell memory in matched-pair kits for utilize in systems that hold dual-channel memory.