If I'm not mistaken UMA settings in BIOS refer to how much and how memory is allocated to the motherboard integrated video hardware. I doubt that's going to magically make your external solution work. I could be mistaken of course, but I'd be looking for other potential issues/settings. Regular desktop board often have initialization priority settings, but I don't know if or how many portable devices would have such a setting in their BIOS. By the way, your link doesn't seem to work.