NVIDIA GeForce GT 640 's Advantages
Lower TDP (65W vs 165W)
NVIDIA GeForce GTX 980 's Advantages
Released 2 years and 3 months late
Boost Clock1216MHz
More VRAM (4GB vs 2GB)
Larger VRAM bandwidth (224.4GB/s vs 28.51GB/s)
1664 additional rendering cores