Both cards have a 256-bit memory bus with a bandwidth of 224GB/s and 4GB GDDR5 memory for the reference models. Due to energy efficiency enhancements the GeForce GTX 900 cards have just a 6-pin + 6-pin power connector instead of the 6-pin + 8-pin seen on previous generation high-end cards.
Official details are expected to be revealed on September 19th but the current rumor is that the GeForce GTX 980 has a TDP of around 175W whereas the GeForce GTX 970 has a TDP of just 148W.