OTOY Forums

I have a gfx 660ti card.
should I be using cuda version 5 ?

Your card is a fairly recent one.
All Nvidia drivers available for this card have been cuda 5.
Cuda is backward compatible.
Your driver should be fine for Octane v1.0 and previous RC
Btw drivers for the 660ti are from 305.68 onward.
HTH

Separate CUDA toolkit install was required (only) on Linux, but it's not anymore. So just grab the latest stable drivers for your card.