I have win 7 ultimate 64 and an ATI 3450 connectet to a monitor (DVI) and a toshiba 37rv TV (HDMI). I am using the latest catalyst drivers.
The image on the tv did not cover the whole area, showing black bars on the 4 edges. So I changed the "scaling option" from the default 8% to 0%.
However, at 0% I have the opposite problem, i.e. a bit of image goes "outside" the TV visible area. The setting that looks the closest to a 1:1 representation seems to be a scaling option of 5%, but still that's not perfect, i.e. I don't get a pixel per pixel image (I tested that looking at an image made of black and white lines with width of 1 pixel)
I have similar problem. The only difference is my TV - Samsung UE55B7000. I've been searching through the forums for last few hours, but it seems as people don't realize, that it isn't only the size of the picture that matters, but also resolution! They're advising to use the overscan, but this just stretches the picture and don't adjust the real resolution.
Partial solution was activating ATI's "optimized" mode, and the picture on the TV is perfectly clear, but this reduces the resolution to 1776x1000 (really weird), so there are still black bars around the edges! Another weird thing is that the TV automatically activates different color profile - going from really ugly colors in fullHD to nice warm in 1776x1000.