can run starcraft 2 on ultra but not RA3!!

[Karlos1544]

Hi everyone, i really hope you can help me. i have tried seraching for a solution first but cant find anything...

Basically, i have recently set up an external graphics card and have been getting good (ish) benchmarks. 3Dmark06 over 12,000, 3dmarkvantage GPU score over 14,000, Resident evil 5 variable benchark over 80 fps in dx9 and dx 10.

All this means i can play starcraft 2 with setting on ultra settings with very little lag.

But when it comes to RA3 it wont run well at all!! i have to make most setting medium and it still lags horribly approx to 10 to 15 fps in battles, especially on water.

does anyone know why i cant run the game properly? i have openGL enabled on my card, could that be causing a problem

I play on PC and my rough specs are

windows 7, 64 bit
core2duo 2.66 Ghz
4GB ddr3 RAM
Radeon HD 7850 2GB

I dont have the diagnostics output, sorry, beacuse i sent my card back to the shop, but i m reluctant to replace it if it cant even run a four year old game.

i d really appreciate any help!