FPS problems with Crossfire

[jcaulley74]

I am having problems with Oblivion and my Crossfire setup. I have an Alienware M17x with an i7-720 processor, 2x 1gb ATI mobility 4870 video cards and 4gb ram. If I run Oblivion as windowed (1920x1200) no mods, all detail settings maxed, HDR on, no AA, I get around 45-50 fps while inside a city. In the windowed mode, only one card is handling the game as is evident by the 68 degree temp of the primary card and the 42 degree temp of the slave. If I launch as a full screen (1920x1200) exact same settings as above, my frame rates drop to 35-40 fps. Both cards seem to be assuming some load from the game, both cards go from their idle temps of 42 degrees up to about 57-59 degrees. This doesn't even cause my cooling fans to kick into high. So while it appears from a hardware perspective, it is trying to use crossfire, I am getting decreased performance when in this mode. I have tried a few of the "rename the .exe file" tricks and this has not helped. I know that crossfire does function properly on the computer on other games. I regularly play EVE Online and going from windowed to full screen will improve my frame rates from 80 to 165. Has anyone else run into any issues like this? I am running out of things to try and I am finding it crazy to run in a windowed mode to get better performance. I am running a standard DVD installation (not Steam, not GoTY edition). I do have Shivering Isles installed and the latest patch. Any help would be greatly appreciated.