a) They have, ATI implemented Brook+ b) GPUs are still first and foremost special purpose hardware. Few applications are benefitting from moving all your data

a) They have, ATI implemented Brook+ b) GPUs are still first and foremost special purpose hardware. Few applications are benefitting from moving all your data over to your graphics memory, pushing it through a broad but slow pipe and copying everything back to your CPU. You need to pull out all the low-level stops to get the most out of the hardware, which means dealing with really low-level libraries. CUDA has something like 7 types of memory locations you can declare for your data to sit in and some are calling OpenCL too abstract.