External Monitor on M17x ATI 4870

I recently got my M17x ATI Rad 4870, and while at home I plug in to a 27" SamSung Syncmaster P2770H monitor (60hz, 1080p HMDI) as my primary display.

However, while gaming (StarCraft 2 Beta) I have to lower the in-game graphic settings to the LOW accross the board, because the framerate is so terribly choppy while on MED or HIGH, and completely unplayable on ULTRA.

In the ATI CCC I have played with the settings and have produced no substantial changes to this problem (ie, going for 'performance' settings in basic terms).

Question 1: Is using a display of this size just TOO demanding for the 4870?

Question 2: Any suggestions on settings I may be able to change that could improve this?

Question 3: If upgrading is the only solution, would a single 5870 do the job? Or would a 5870 Xfire be required?

 

I would check to make sure you aren't in stealth mode, and make sure Powerplay is on (in your Catalyst control center), and that your power settings are set for high performance.

The display size has nothing to do with it, just the resolution, which as you say is 1080p, and assuming you got the better screen for your M17x, it has a 1200p screen which would actually be more demanding than 1080p.

The game should be able to run better than you described (I've never played SC2 so I don't know for sure but I've heard others post here that it runs fine), so that's why I believe something else is the issue