The way I came up with the 1280x1024 minimum is that I found on my 4870 that it did not overheat or crash if I ran FurMark at anything less than 1280x1024 in the stability test. 1280x1024 or higher would cause the temps on the VRM to skyrocket and the card to crash. I guess it is a personal experience only...I just went by it anyways. I do agree though that if your GPU load while running ATITool and FurMark in your setup is at or very near 100% for the whole duration that is then good enough.