Help me Understand how DDRII works.

Ok, I under stand how DDR works, double the data for each cycle giving you double the clock speed. example: 200mhz=400mhz FSB. But how does DDRII work? how does 133mhz give you a 533mhz fsb? Also, how is it that DDR 667 will allow for a 1066mhz fsb? thank you.

On most motherboards these days memory (be it DDR, DDR2, or anything else) are 'dual channel'

Each DDR memory channel is 64bits wide, taking DDR2 533 as an example the bus runs at 266mhz, with 2x64bit transfers per cycle.

With dual channel running syncronously, then you have an effective 128bit bus, so you can now transfer 4x64bits per clock cycle.

A Pentium, or Core 2 processor has a 64bit frontside bus, running between 100mhz and 266mhz depending on the model. As its 64bit bus can do 4x64bit per clock cycle, thats why motherboards need dual channel ram to keep up.

AMD have the memory controllers built into the processor, so they have 2 64bit memory busses running at DDR rates, I dont know what clock frequency's can be selected on the AMD memory controllers.

QDR memory is in development, but I believe there are some Patent issues allow Rambus to hold up the work.