That´s true Luciel both things have nothing to do with each other.
The graphics card administrates itself and the DDR-Ram on the
mainboard does so.

The graphics card works independant from the cpu of the pc.
After 1 hour of investigation I came to the conclusion that this
case is for an expert or even a small genius as I can´t find any
clear explanation in the net.

I would also like to add, that you can use even a ddr3-ram graphics card
with a ddr-ram mainboard.