Okay guys, the key to getting good HDTV display from a computer is in the signal timings. Here's why. The video card is used to sending it's RGBHV (Red, Green, Blue, Horiz Sync, Vert Sync) signal from the VGA connection to a computer monitor, which will follow the sync signals and display virtually any resolution and refresh rate (within it's limits). HDTV's on the other hand, expect the information coming in to be in an HDTV format (480i, 480p, 1080i, or 720p). Any other rate that it can't immediately recognize as one of these, gets sent to a reprocessor, that will take that input, digitize it, and attempt to scale it to fit the screen. Different TV's do this with varrying degrees of success. The best solution would be to ensure the computer is always outputting an standard HDTV signal, so the picture doens't get scaled, and one pixel sent from the computer is displayed as just one picel on the screen (1:1 pixel ratio). This takes the use of 3rd party software that will allow direct manipulation of the horizontal and vertical refresh rates of the video card. The most popular software for this is PowerStrip. Basically, this software allows you to add custom resolutions and fix resolution to specific timings. My set (A Phillips Cineos 55" LCoS) is natively 1280x720x59.97 Hz, but because of the overscan, i had to create a custom resolution of 1240x700 to get the display to be fully visible (though the timings had to be the same as the default 1280x720). The timings I use are as follows:
Horizontal geometry
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Scan Rate 45.055 kHz
Active 1240 pixels 16.700ìs
Front Porch 104 pixels 1.401ìs
Sync width 40 pixels 0.539ìs
Back Porch 264 pixels 3.556ìs
Total 1648 pixels 22.195ìs
Vertical Geometry
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Refresh rate 60.073 Hz
Active 700 pixels 15.537ms
Front Porch 13 pixels 0.289ms
Sync width 5 pixels 0.111ms
Back Porch 32 pixels 0.710ms
Total 750 pixels 16.646ms
This works for me, but, every HDTV has different tolerances, and may need to be tweaked to work with your particular display. The way to check and see if you are truely getting a 1:1 ratio is to create a small 4x4 bitmap in Paint, of a black and white checkerboard pattern, and set it as the desktop background in tile mode. If you can see the crisp checkerboard spread across the screen, than the tv isn't scaling. If the checkorboard is blurred to a slight grey instead, then the timings are not being seen as HDTV. If this is set up correctly, you will be quite impressed with the clarity of the text, as it should be every bit as readable as on a computer monitor.
DVI may not always work, as DVI is 2-way, meaning the tv can tell the video card what resolutions it supports, and usually these are just the standard computer resolutions (640x480, 800x600, 1024x768). These will always result in scaling. Again, all tv's are different, and yours may behave differently.
Hope this helps,
CraziFuzzy