You loose half the resolution since each eye needs to be looking at the same thing. Second since you're looking at it in stereo you need to have the desktop a d

You loose half the resolution since each eye needs to be looking at the same thing. Second since you're looking at it in stereo you need to have the desktop a decent enough distance away from you to be able to focus on it or you'd go cross eyed. I think this is what causes the effective resolution to drop to that much lower level.