How much memory is the intel GMA 4500mhd able to share?

For a laptop or tablet (the moble eddition of the GMA 4500mhd), i was wondering the max amount of memory that it can use from the system ram inaddition to it small onboard ram. how much onboard does it have. does any one know what it scored in vista's windows experience index. the chipset is the moble G45 express chipset. thanks for answering.