AGP Mem allocate

Hi All
I wanna put a texture into the AGP memory using OPENGL, but i can not find a way to do it.Does ATI card support this feature?(I am using ATI Radon9500)

Any suggestions?
Many thanks in advance,
Yours Heron

Any specific reason for this? Otherwise, the driver gets to pick where to put it, or where it should be moved.

Yes,this texture should be accessed by CPU and update every frame.