If you buy the dv9500 with the 8600 GS GPU you get 256 MB of discrete gfx. The configurator says 511 MB of GPU memory but 255 MB of that will be shared with the system memory.
511MB NVIDIA GeForce 8600M GS
The NVIDIA(R) GeForce(R) 8600M GS delivers unparalleled levels of graphics realism and performance. If configured with the 1GB DDR2 System Memory (2 Dimm), there will be 256MB dedicated memory and up to 255MB shared memory. If configured with the 2GB DDR2 System Memory (2 Dimm), there will be 256MB dedicated memory and up to 667MB shared memory. Key Features: Fully unified shader core dynamically allocates processing power to geometry, vertex, and pixel shading operations, enabling life-like realism?even in complex scenes. Completely unified and optimized for current DirectX 9 and next generation Direct X 10 games and applications. NVIDIA Lumenex(tm) engine delivers incredible image quality, floating point accuracy, and fast frame rates. DISCLAIMERS: Shared video memory (UMA) uses part of the total system memory for video performance. System memory dedicated to video performance is not available for other use by other programs. NVIDIA and GeForce are registered trademarks of NVIDIA Corp.