I'm currently evaluating to buy a 4K computer screen to use in 2160p natively while coding or working with Windows but I plan to play my games in 1080p because 4K rendering is of course a very heavy job to do for any CPU&GPU. Currently I'm very happy with 1080p gaming and it would be great for me to have one single screen in those two modes.
However, I know that the upscaling algorithms are not just "1px in 1080p equals 2x2px in 2160p - so everything would be fine ..." as it is told in many forums. That's just wrong because normally the screen image gets blurred depending on the upscaling algorithms the GPU and/or the screen are applying.
Now, I stumbled upon nvidia's Dynamic Super Resolution technology and I wondered (but I could not really find out) whether it (or any other tech) can be used to tell the GPU to render a 2160p image exactly by bloating up a 1080p image to the doubled size per side . So that there's no need to interpolate any pixels and the 2160p-image would just look as crisp as the 1080p on a 1080p-screen (of course with the same non-4K-amount of detail).
Please have a look at the attached image I have stolen from http://linustechtips.com/ and extended with my comments:
EDIT: I know that DSR is supposed to perform downsampling high-res images to a lower-res screen. So it is the opposite of what I wanted to have. But maybe the nvidia driver can do the other way round as well (maybe it's not called DSR then but I don't know).