Hardware Secrets posted an article on RAM Timings
DDR and DDR2 memories are classified according to the maximum speed at which they can work. But, besides the speed, there is another information that tells you the memory performance: timings. Timings are numbers like 2-3-2-6-T1, 3-4-4-8 or 2-2-2-5, the lower the better. In this tutorial we will explain you exactly what exactly each one of these numbers mean.Understanding RAM Timings