Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
well it depends on what you want to do with it, are you wanting to use it as the primary monitor, with the onboard LCD being, mirrored or secondary? if you use it mirrored the onboard LCD will go down to 1650x1080 to match the external, if you have the onboard be secondary it will maintain its native aspect ratio
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.