[moenchmeyer]

I should add that the graphics card reacts when disconnectiong the power cable.

Then it reduces clock speed to performance level 2 - and remains there. It never reduces to performance level 1 or 0.

I.e., when using battery power it runs constantly at
Graphics clock = 383 MHz, Memory Clock = 301 MHz, Proc. Clock = 767 MHz

As soon as the power cable is attached again the graka runs constantly at performance level 3.