Does Video Memory Size Matter?
This section is the most difficult one to write, the problem is that there aren’t that many good performance tests for a high end GPU under OS X. It also happens to be a big part of the reason Apple can get away with shipping integrated graphics in the majority of its machines and a low end add in card in its Mac Pro. Honestly, one of the biggest uses for a new graphics card under OS X is having additional video memory. The contents of each window and the windows themselves are drawn by the GPU and stored in video memory. Previous versions of OS X either drew windows in system memory and then composited all of them in video memory, or did everything in system memory and just outputted the final scene to the video card. Ever since OS X 10.4, the entire drawing and display process happens on the GPU and in video memory. Ars Technica’s John Siracusa has an excellent explanation of the whole process. Each window gets treated as a 2D OpenGL surface and all of the character and image renderi
