What is the motherboard???
AGP 2.0 is a 1.5V AGP slot capable of 4x,2x and 1x speeds. AGP 3.0 (8x) is keyed like a 1.5V AGP 2.0 slot, but it only uses 0.8V of power.
It supports 8X, 4X, 2X and 1X speeds.
AGP Speeds are required to be backwards compatible. This means that an 8X video card MUST be able to run at 4x, 2x, or 1x speeds. However, this does
NOT necessarily mean that your 8X card will run on a 4x slot.
Because speeds must be backwards compatible, Signalling Voltage is where incompatibilities arise.
The bottom line is ... your 8X video card can theoretically be safely
TESTED in any 1.5V motherboard for compatibility. But if you know for a fact that your board
only runs 1.5V
AGP 2.0 spec and the 8X AGP 3.0 card runs
only 0.8v spec, then the two should NOT be compatible with one another. At the very least it will be unstable, if, it runs at all.