I tried the first sample from the book "OpenCL in action" by Matthew Scarpino.
The code finds the devices installed and runs a matrix multiplication (4x4 * 4x1)

The device I have is NVIDIA's "GeForce 9400 GT". I know it from: clGetDeviceInfo
The platform I have is: NVIDIA corperation. I know it from clGetPlatformInfo

But currently I'm using AMD's SDK.

And it works !
1. How it is possible ?

2. Will I get better performance if I used NVIDIA's SDK ?