To run the 4870X2 through its paces, we are going to run a plethora of benchmarks.  Now, GPU benchmarks generally fall into three different classes, all with different strengths and weaknesses:

Synthetic: These benchmarks are generally not tied to any specific game, but are generally designed to emulate what gaming can be like.  If the benchmark is universally accepted, it can be used as a rough guideline as to performance.  The downside is they are a poor judge for any specific game title.

Timedemos:  Time demos are usually pre-recorded sequences within the game that are replayed, and the performance measured.  The advantage of time demos are that runs are exact every time, and should give a good measure of a games performance.  The disadvantage is that not everyone owns all the games.

In Game Frame Counting:  In game frame counting usually involves the tester playing the game, and using a tool like FRAPs to capture the frame rate.  The advantage here is that actual game play is being used, the disadvantage is that it is hard to duplicate the exact same sequence more than once. 

In order to paint the most complete performance picture, we will be using all three methods.  And in order to make things interesting, we are going to compare the X2 to the reigning champ: a factory overclocked MSI GTX-280, all on the following test bench, using Vista SP1: