So I'm having the same issue. However my machine is not using all cores and is rendering very slowly. I have a mac pro running os 10.9, 2 x 2.4 GHz 6-Core, 64GB RAM, and my graphics card is an NVidia Quadro 4000 with Cuda version 5.5.28. I've looked for updates, but everything seems to be current. Not sure what I should do?
| Fast Draft: | Available |
| Texture Memory: | 1515.00 MB |
| Ray-tracing: | GPU |
OpenGL
| Vendor: | NVIDIA Corporation | |
| Device: | NVIDIA Quadro 4000 OpenGL Engine | |
| Version: | 2.1 NVIDIA-8.18.22 310.40.05f01 | |
| Total Memory: | 2.00 GB | |
| Shader Model: | - |
CUDA
| Driver Version: | 5.5 |
| Devices: | 1 (Quadro 4000) |
| Current Usable Memory: | 691.00 MB (at application launch) |
| Maximum Usable Memory: | 2.00 GB |