Opencl implementation of convert_char()

I am using Intel core i7 6820HQ CPU and integrated graphics 530 to run an opencl application.

When I perform convert_char() on overflowed results, I get different results in CPU and GPU.

E.g convert_char(271.125) on CPU overflows and rounds up whereas in GPU it clamps to 255. ofcourse by doing convert_char_sat() i got the right results on both platforms.

But can someone explain why it works differently on different platforms?