I have 2x5870 in crossfire at 1920x1080 resolution. I had the card in slot 1 hook to monitor with hdmi. I noticed at the start of fear 2 before it got to the game screen that it had faint lines going up and down the screen like it was scanning. I mean it wasnt bad but I could see them. I decided to hook up the dvi cable to see what happened. The lines went away and gave perfect video at the start of the game. I thought there wasn't any difference in hdmi and dvi besides that hdmi carries audio??
Also do I need a video cable hooked up to the second card? I just use 1 monitor.
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Also my monitor is 23.6 inch Asus VH242.
It is likely that the hdmi cable you were using, or the port itself, is simply flawed in some way.