Typically when you install memory in a system, there is a set of standardized speeds/timings your memory will run at, this standard is what we call JEDEC. This is why you see DDR3 memory speeds like 1066MHz, 1333MHz, 1600MHz, 1866MHz; these are standardized speeds that all memory manufacturers adhere to.
Outside of JEDEC, we have something else that can determine the speed at which your memory runs, and this is XMP. Extreme Memory Profile (XMP) was originally created by Intel and is now used by all memory manufacturers with high performance desktop memory. Unlike JEDEC, XMP speeds are higher performing, and are usually custom tweeked to the specific needs of the memory. When you purchase XMP compatible memory, you must also pair it with an XMP compatible motherboard, and a CPU that will support the memory speeds. Typically XMP must be manually enabled in the BIOS settings as well.
So what happens if I install XMP memory in a non-XMP motherboard, or I don’t have XMP enabled?
Well the memory will simply run at whatever JEDEC timings the computer decides. With Ballistix parts this often means the memory will be downclocked to the next lowest speed; so a pair of 1866 MHz Ballistix Sport parts could run at 1600MHz if XMP was not running as an example, or it could run at 1866MHz but with a slower latency. This is all okay of course, since most of our memory is designed to run at multiple speed settings, so even if your memory doesn’t have the frequency or timings that are listed for it on our website, it will often run flawlessly at those parameters.
So to sum things up: XMP is a great way to get extra performance out of higher end memory, if you have a setup that will support it, otherwise it’s an additional feature which is not required for the memory to operate.