Unrecognised NVIDIA GPU in LInux Mint

I’ve been using Blender for about two years now but I’m new to Linux.

I’m using Linux Mint 17 Cinammon (64-bit) and an NVIDIA Geforce GTX 850M. The OS came with a driver for the graphics card and some CUDA packages, but GPU was not an option in User Preferences. I also read that these unofficial drivers have a lower performance than the official drivers, so I installed the official driver (version 340.46) using the tutorial at youtube. com/watch?v=AkKkuzWlaGo (remove the space as I don’t think I can post links yet). There was still no CUDA or GPU option in Blender, so I installed the CUDA toolkit version 6.5 (which I was under the impression I already had) using these instructions: sn0v.wordpress. com/2012/12/07/installing-cuda-5-on-ubuntu-12-04/ (I used the Ubuntu 14.04 toolkit from developer.nvidia. com/cuda-downloads). I ensured the CUDA samples could find the libraries they requested (different since the tutorial for CUDA 5 was published) but still had no luck with Blender. Whenever I say blender I mean both 2.69 from the software manager and 2.72a from blender. org.

I can see from the NVIDIA X Server Settings application that the GPU is working, as the percentage GPU utilisation goes up when I drag windows around and goes up to 90% when using Blend4Web (which may be a good sign seeing as it is based on Blender - no idea if Blender handles the rendering though).

It’s been a large struggle getting this far and I don’t know what to try next. Any help would be much appreciated.