Depending on your system, you can specify the bit depth for images that are processed using the frame buffer in the graphics card. The bit depth affects the quality of the resulting clip. Images can be processed with 8-bit or 16-bit FP precision.
As a rule, if you are working with mixed resolutions and some clips are higher than 8-bit, you should select 16-bit FP graphics display. Even if you work only with 8-bit images, you can get better processed results with 16-bit FP graphics processing when transparencies, blending, and gradients are part of your effect. 16-bit FP graphics processing produces better results but takes longer.