Remember that 2x 512 gpu's at say, 550Mhz and 1v, and 2x448/480sp's at an increased clock with increased voltage could perform the same, but the 512sp's with lower clocks and voltage would use less overall power.
Theres a reason that in general all the dual gpu cards have two full cores on, downclocked, and not two lower end cores with higher clocks. You also get more full yield parts in the centre of the wafer which, 98% of the time will have the best power consumption profile.
Its almost certain to be a 512sp cores, or 384sp's on a 560gtx core, or of course, not arrive at all.
I'll point out again that AMD have confirmed the 6990 on numerous slides, while Nvidia haven't mentioned a dual gpu card AT ALL.
A pcb shot quite literally means nothing, for years we've seen them for multiple "theoretical cards" that never make it to market, last year we saw a dozen different dual gf1014/gf100 cards and a grand total of none made it to market.
The only card off the top of my head I can think of that didn't use full sp cores was teh 4850x2, which got zero traction as the power saving it offered was almost non existant, highly binned central wafer full SP cores vs 4850 cores with failed SP's and higher effective clocks for any given performance level. Every successful dual gpu card had all its cores available, 295gtx, 4870x2, 5970, etc, etc.
