Probably system or driver issue resulting in lending/grabbing the maximum amount for no reason. Performance-wise, 4 GB dedicated video card gets no benefit from

Probably system or driver issue resulting in lending/grabbing the maximum amount for no reason. Performance-wise, 4 GB dedicated video card gets no benefit from those extra gigabytes in RAM buffer anyway. Do Quadro cards support some kind of “fat and slow” compatibility mode for software that demands giant memory size on a professional card to fit all the data there, and can wait to get the results? Maybe there's some switch you've toggled to enable “20 GB VRAM” mode?