Myths that won't die …

Mac OS X virtualizes video RAM and will NOT partition it between two monitors, even if some older tools claim otherwise. Video RAM gets assigned to whatever needs it, so with two monitors connected an application can still use nearly all of your 256 MiB (minus the frame buffer for the second monitor, a few window images from Quartz Extreme, etc). Core Image and Quartz GL should be able to make good use of all the free VRAM.

MacOS 9 did split the VRAM between two active monitors. These different behaviors can be seen with "ATI Displays" on Radeon cards under both systems.

MacBook Pro 15" (Santa Rosa based) @ 2,2 GHz

Recently I had access to a new MacBook Pro which is capable of running the enhanced OpenGL test:

CINEBENCH R10.1
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Tester           : Pareis

Processor        : MacBook Pro 15": Core 2 Duo T7500, 3 GiB 667 MHz DDR2 SDRAM
MHz              : 2200 (running on power adapter with better performance)
Number of CPUs   : 2
Operating System : Mac OS X 10.5.4 (9E17) -- [updated results with small improvements]

Graphics Card    : NVIDIA GeForce 8600M GT, 128 MiB
Resolution       : 1440x900
Color Depth      : 32 bpp

****************************************************

Rendering (Single   CPU): 2407 CB-CPU 
Rendering (Multiple CPU): 4520 CB-CPU 

Multiprocessor Speedup: 1.88

Shading (CINEMA 4D)                :  427 CB-GFX 
Shading (OpenGL Software Lighting) :  718 CB-GFX 
Shading (OpenGL Standard)          : 4388 CB-GFX 
Shading (OpenGL Enhanced)          : 1025 CB-GFX

OpenGL Speedup: 10.28

****************************************************

OpenGL Enhanced Test
40.597 sec; 9.0 fps

OpenGL Standard Test
9.480 sec; 38.5 fps

OpenGL Software Lighting Test
57.949 sec; 6.3 fps

CINEMA 4D Shading Test
97.492 sec; 3.7 fps

Single CPU Render Test
367.4 sec

Multiple CPU Render Test
195.6 sec

OpenGL Enhanced uses hardware shaders to render the scene with realistic lighting. Its requirements can be verified in the benchmark under File / Preferences… / Viewport / Show OpenGL Capabilities.

The added tests and verbose output (copied from the Console pane) require modifications to the file Bench.cof (available for download). This file belongs into the plugins subdirectory of CineBench R10. A diff will show that most of my changes are nothing but uncommenting inactive instructions.