I currently have the rig that is listen below \/ I have a small 15" 1024x768 VGA Flat Screen Monitor. I am getting a Acer 20" 1600x900 DVI monitor on Friday. I am wondering if FPS in games will drop alot from this resolution increase. I do not want to have dual displays because the 3870 heats up very well with 2 monitors.
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The 20" screen has twice the pixels of the 15" screen. So yes, your performance would drop considerably. But the 20" screen isn't very big itself so a 3870 should be enough for medium settings for many games.