I don't remember paying attention much to whether oblivion supported sli/cf, but did it? I could max it out either way. The reason I ask is that Skyrim has to have crossfire/sli support or I'm gonna be pissed.

The software does not need special instructions for crossffire and sli to work, only your motherboard needs to support the architecture. They are both modes that alternate drawing frames of animation between video cards so that card 1 does every odd one and card 2 does every even. That splits the work load in half and results in as much as 2x the framerate depending on the workload required to produce the images. So you do not need to worry about Skyrim supporting either.

Some games support crossfire and some don't. For example Mass effect 2 supports and scales well with crossfire while games like half life are no good.

As I understand it both Crossfire and SLI and not dependent on the game. It is a function of the motherboard and drivers. Nothing special needs to be written into the game.

The HW/SW forum may have more extensive answers. I'll request a move.

The game really doesnt use Crossfire/SLI very well. In some cases wont even start up when the second card is enabled. When I used to run dual ATI 4890s in Crossfire, it would crash on launch all the time.

The game engine needs to be capable of instructing the computer hardware how to perform the SLI rendering correctly, though. SLI/Crossfire is not a plug-n-play feature like so many people want you to believe; it relies just as much on the engine of the software it is rendering for as it does your hardware. Oblivion does not have this capability, and my attempts at using SLI in the game have actually caused performance to degrade as a result of it.

Oblivion works best on a single GPU.