Information about buy GPU


In January, I bought the GPU - GTX 690. However, I am not satisfied with the buying because I thought that I could use with a single GPU, 4GB of memory. Thus, the GTX 690 card integrated 2GB memory for each GPU. A single GPU may be unable to fully access 4GB memory.

I would like a help because I will exchange this GTX 690 for another GPU. In this case,I work with:
1 - CUDA (Cusparse and Cublas);
2 - double precision;
3 - high memory, because I work with very large matrix (Ax=b)(vector x with 1 million of the elements);

Best Regards,

Ana Flávia.