According to info from NVidia website https://developer.nvidia.com/cuda-gpus, GTX460 supports CUDA version 2.1.
Referring to http://en.wikipedia.org/wiki/CUDA, it seems to suggest that CUDA 2.1 only uses 48 cores for integer and floating-point arithmetic functions operations. (Correct me if I am wrong)
I wonder whether the dismay result of GTX460 is due to the low CUDA version, limited graphic memory or the nature of the simulation performed.