We already told you here that RV670 was the first A11 silicon that was ready for production, and in the graphics world, A11 is the first silicon. The original plan was to launch RV670 based cards in early to late January, but as the hardware was ready ATI had to launch as soon as it could.
This has set R680, dual RV670 cards in quite an awkward position, as the hardware is ready but not the software. Quad Crossfire of Crossfire X, what ATI calls this marchitecture these days, driver will be ready and launched in January.
Currently, you can make two Radeon 38x0 cards work together in Crossfire, but for three or even four cards, you will have to wait until January.
Radeon 3870X2 to scale up to 300+ percent
R680, Radeon 3870 X2, detailed pics
RV670 A11 silicon works well
R680 is Radeon 3870 X2, cards pictured