Quote Originally Posted by dexx
But wouldnt this (eg 7.8ns) only be applicable at SPD eg at 200MHz. How do we know that it isnt 5.6ns at 300MHz?
The refresh rate needed isn't based on the frequency you're running at

DRAM cells (individual bits in the memory) use a capacitor to "remember" the data (specifically to remember 1's... discharged capacitors are 0's). There is leakage in the cells and over time the capacitor "slowly" looses it's charge if it isn't refreshed... and the data gets corrupted (changes). During a refresh cycle, the data is read out of the memory cells and then written back... renewing the charge on the individual cells' capacitors.

Peace