Thanks for the heads-up.
Where can we source the Intel information?
Asus: ASUS 'solution
ASUS has the P7P55D-E motherboards figured out another solution. On these boards we find a special chip that PLX PCI-Express lanes can combine up to 1.1 speed lanes on 2.0 speed.
The figure below shows the implementation in detail. The 16 lanes from the processor go by the book, so all the video card can work at full speed. From the P55 chipset to four lanes to the special PLX chip. These lanes so work on 1st generation speed, but 4 x 250 MB / s in total natural 1000 MB / s. The PLX chip in turn transforms to x4 PCI-Express 1.1 to double PCI-Express 2.0 x1. The entrance is 1000 MB / s and output two times 500 MB / s. The USB 3.0 and SATA3 chip are both so driven by their maximum speed, while there is no delay in the video card.