These settings are generally in the BIOS but Toshiba, as I recall, tends to restrict user access to these features. It's possible there's an option for this in the latest ATI drivers if you download them from their site.
ATI integrated video also adjusts the amount of memory it uses on the fly. So it will use more while you're playing a game in order to maximize performance, less while you're surfing the internet or burning a CD.
My Laptop GFX card 
Linear Mode
