shane799 said:
Hey
I'll let you explain that to my wife. Sorry this won't be the most technical explanation. The first card does all of the work until more processing power is required at which point the 2nd card kicks in.
You don't double your memory. If you have 2 1 GB cards you don't run 2 GB of GPU memory you only still have one GB in use. The 2nd card helps render more graphic power when required. You get to use the extra shaders and stuff.
As far as your end power with 2 5770's you end up equivalent to a 5870 or 6950 in many applications. Before people start debating this...yes a single 5870 is a better solution. Thanks ahead of time for pointing this out! With 2 5770's you will be able to play pretty much anything at the top resolution with great frame rates. Except 2033. That game is optomized REALLY poorly. I have to drop to 1680 for that one.
A couple things that need correcting here. If you have crossfire enabled and in an application that will use crossfire, crossfire is used on the 2nd card. It has nothing to do with the game needing more power than 1 card can handle, it just uses it and give you FPS beyond what your monitor can display.
If your CPU or another part of your system is holding back the ability to generate frames, both cards will have their workloads lowered. Generally they will show very close to equal loads at all times, even if at 50% workload. The same thing happens when you enable V-sync, since you cap the FPS at your refresh rate (usually 60hz).
Metro 2033, from my perspective, is optimized extremely well. Not only does the game push the limits at it's highest settings, and looks amazing, doing things no other game does with visuals, but at low settings, it does a remarkable job at loading pre-calculated routines to make a very attractive looking game even if your system can't do everything the very best systems can.
Just because a game can use and require the top of the line hardware to handle it's best settings, does not mean it's poorly optimized. It often means they add more visual levels. A good example of a REALLY poorly optimized game, would be Gothic 3. While it looks ok, it requires far more hardware requirements than games that look better.