When I read that the GTX 960 has a TDP of 120W I got a little suspicious, considering that the GTX 980 is only rated at 165W. It seems that the GTX 960 does not use a fully-enabled GM206. I am not the first person to say this, though, as this point has been raised many times before in the media, along with the discussion around a potential GTX 960 Ti. What I want to do in this post is to present some quick numbers that seem to support that claim.

I focused on three metrics: number of CUDA cores (Unified Shaders), transistor count (in millions) and TDP (in Watts), and three (presumably fully-enabled) Maxwell cards: GTX 750 Ti (GM107-400-A2), GTX 980 (GM204-400), and GTX Titan X (GM200-400). I then calculated # of CUDA cores per Watt and # of transistors per Watt  for each card. Results are shown in the table.

For some reason the GTX 960 is noticeably lower than the rest of the group, as you can see. In the GPU world, it is often the case that power consumption stays largely the same even when some computational units are disabled, which could explain what’s happening here if GTX 960 is indeed a harvested GM206.

Card CUDA Cores TDP Transistors Transistors/Watt CUDA Cores per Watt
GTX Titan X 3072 250 8000 32 12.3
GTX 980 2048 165 5200 32 12.4
GTX 960 1024 120 2940 25 8.5
GTX 750 Ti 640 60 1870 31 10.7

6/20/15 Update:

Considering that the R9 380/285 is not a fully-enabled Tonga on the AMD side, it seems even less likely that GTX 960 is a fully-enabled GM206.