on the gigabyte board its in the bios under IGX configuration wich is located on the M.I.T. screen
UMA Frame Buffer Size
Frame buffer size is the total amount of system memory allocated solely for the onboard graphics controller. MS-DOS, for example, will use only this memory for display. Options are: Auto (default), 256MB, 512MB, 1024 MB.
so no its not hardwared per say, but may be different for each motherboard. you didn't say wich board you have so if its not the gigabyte, youd have to look it up.
It's an MSi board, Its set at 512mb by default on it so I think that will be fine until I get discrete graphics.