GPU
Fred's Fractal Factory can use the GPU to calculate Mandelbrot and Julia Escape Count values.
The GPU selection allows you to select the Graphics Processing Unit used by Fred's Fractal Factory. Fred accesses the GPU via the OpenCL library, so the OpenCL drivers must be installed on your system. Which OpenCL drivers are installed on your system generally depends on which vendor made you video graphics hardware. The GPU and OpenCL library that you select must support double precision arithmetic. If your selected GPU does not support double precision arithmetic, then Fred will tell you so, and then revert to calculating with the CPU. Fred works fine if no GPU is available, but it runs slower.
If Fred cannot find a GPU via the OpenCL library, then the only selection available will be 'GPU NOT USED'. Fred's Fractal Factory will default to using a GPU if it can find one.