As usual, only way to be sure is to use a multimeter. Measuring core voltage on a video card is easy and the methodology remains the same for years and years. All you need is one multimeter probe on your computer case, one multimeter probe on one of the core VRM inductors or capacitors (often through-hole which makes it even easier), and experience knowing how to use a multimeter and identifying VRM components.

Actually, all he needs is a multimeter.