Locating the VRAM information on your Mac
To locate the VRAM information on your Mac computer:
In the Apple menu, select About This Mac and then click the System Report button.
In the System Profile window, under Contents, select Graphics/Displays (for Mac OS X 10.4 "Tiger and higher) or PCI/AGP Cards (for Mac OS X 10.3 "Panther"). If available, the amount of the video memory appears next to VRAM on the right side of the window.