Anandtech published a review on the ATI Radeon HD 3870 X2
>> ATI Radeon HD 3870 X2: 2 GPUs 1 Card, A Return to the High End
AMD is the first out of the gates with the Radeon HD 3870 X2, based on what AMD is calling its R680 GPU. Despite the codename, the product name tells the entire story: the Radeon HD 3870 X2 is made up of two 3870s on a single card.
>> ATI Radeon HD 3870 X2: 2 GPUs 1 Card, A Return to the High End