Originally Posted by ubikdood
Well, then I guess you'll have to buy an oscilloscope and figure it out for yourself. Good luck.
You're missing the point. The question has nothing to do with what monitor you're using. The question is about a modeline that generates a signal that is compliant with the ATSC specification for 1080i. That's the point of a standard--you don't have to worry about which monitor is implementing it; it it's an HDTV, it should accept and display the signal correctly.
As to the question at hand, my experience with nVidia drivers is that they don't handle interlace modelines correctly.
With 8xxx and earlier, it would accept a 1080i modeline from the monitor (the EDID modes), and generate a working signal, but it would give weird information in the log. Also with 8xxx and earlier, it seemed to be impossible to specify a valid 1080i modeline explicitly--I never got it to work without EDID.
With 9xxx and later, they seem to have changed how the EDID modes are parsed, so they're equivalent to the manual modelines. This means that the 1080i modeline from your HDTV that worked with 8xxx will no longer work with newer drivers, and you're likely out of luck if you want to specify one manually.