GDDR5 can typically do 240GB/s access time on a typical GPU, and there are multiple chips on many cards (Tesla K80). The newer cards use HBM2 and can do 732GB/s (http://www.nvidia.com/object/tesla-p100.html).
Kind of. Nvidia lowered the voltage on their P100 so it does not hit those rates. Theoretically it can go that high, but the power draw was too large. Next gen we'll likely see that.
