The MGHz rating applied to ram is a little misleading as ram itself does not have a clock speed. The quoted MGHz rating instead refers to the speed of the FSB of the motherboard and is the highest speed for which the ram is rated. The figure that really matters, and which most testing programs will give you, is the memory bandwidth which tells you how fast data can written to and read from ram. It is this bandwidth figure which determines how fast the ram actually performs in your system. The "PC" figure, i.e. PC3200, tells you what this bandwidth is. PC3200 means 3200 MBs/second.