[1] The bitmap output from Quartz 2D, OpenGL, Core Image, QuickTime, or other process is written to a specific memory location, or backing store.
Quartz Compositor only accepts raster data, and is the only process that can directly access the graphics frame buffer.
With Quartz Extreme, far fewer central processing unit (CPU) cycles are needed for scene composition.
It then directs the GPU to compose the surfaces and maps to provide the final image, which is delivered to the frame buffer.
Quartz Extreme only uses OpenGL commands, and requires a graphics card connected to an AGP 2X or faster bus (including AGP 4X, 8X, and PCI Express), supporting textures and maps of arbitrary size, since many of the renderers have no size limitation (Quartz 2D for example).