I don't know if this is fully Ubuntu related, anyway here's the question:

After I put in AMD Asus 280X and booted the screen size was normal, but after I downloaded and installed AMD's original 14.4 Linux drivers amd-catalyst-14-4-linux-x86-x86-64.zip, restarted and booted again, it still was full HD but the screen size is like one inch on every side smaller/compressed. It's like as if you open up an image and scale it to 90% or so, you still see everything but you can see if there were text that the text is not in its original size (kind of blurred). (My LG Flatron IPS234 is connected via HDMI with the graphics card, Ubuntu 14.04 64bit)

Here is an image which shows what I mean (note: the camera made this image extreme blurry, in reality it's just a bit blurry):