What?It may have 8GB RAM, but only 3/4s of the memory controllers (6GB card anyone).
No.
It will have something like 3/4 the amount of memory bandwidth due to using GDDR5 rather than the new GDDR5X like on the 1080. But they'll both have the full 8GB available.
I predict this will have a fairly minimum impact at 1080p/1440p.