iMac - Poor performance in SC2

Hmm, that definitely doesn't seem right.
Your iMac should be able to run the game at maximum settings.
Take a look at this link: Notebookcheck 6970M
Granted, the results on the linked webpage were observed when the game was played with a 1920x1080 resolution. However, your higher resolution choice shouldn't be making the game unplayable, and especially not when the settings are at medium.

 

You may have a drivers problem or a bad installation of your game. Try reinstalling the game. That machine should be able to run it with no problems whatsoever.

What version of OS X are you running? Also recommend updating your game if its not the latest version.

 

agreed, i had run this game on my 2010? Early 2011, don't recall, mbp but the point is that it ran smooth. There must be sometbing wrong with either the game or your mac.

 

there is a performance FAQ on the official Starcraft 2 forums:

http://us.battle.net/sc2/en/forum/topic/4079877928

I was having issues with a relatively fresh SCII installation, and following these steps fixed my issues.

 

You will almost always have better performance from booting and running the game in Windows. It's worth installing Boot Camp just for that.

 

games tend to run better on windows still...even blizzard games where the gap is closing but still exists.

 

This is the primary problem. The 27" has too many pixels in native resolution for 1 GB of VRAM. There's no easy way to upgrade it 2 GB (as was available in BTO), but it will make a world of difference in this particular case.

SC2 is also incredibly demanding, and performance in OS X tends to suffer a bit compared to Windows due to insufficient OpenGL hardware acceleration in the GPUs/video drivers. Personally I'm really hoping (but not necessarily expecting) that this gets sorted with this generation and the Nvidia cards.

 

1080p should still look good on the TB display while giving you reasonable fps.

 

Update your drivers

http://support.amd.com/us/gpudownload/Pages/index.aspx

On the right hand side click on the link under 'Automatically Detect And Install'

This will get the latest catalyst drivers for your graphics card and improve performance, AMD claims about a 25% boost but it should run everything better. You can even slightly over clock the GPU using the and catalyst utility, which allows more memory bandwidth and slightly higher clock speeds which will increase your FPS, but I suggest using SMC Fan Control in Mac OSX to rev up your fans to maximum and then booting in windows to play games, that way your mac won't melt when playing games.

 

Just do what I do and play it like the pros do with everything set to low.

 

I was just going to say this.

Have fun trying to snipe a HT with a ghost in a 200/200 battle, or landing those key EMPS against infestor balls, or grabbing that ghost with a Neural parasite.

Much easier to see things on the lowest settings.