tylerk36... you posted to a
link suggesting that hybrid SLI would be supported in 10.5.6. The author speculates that "One could now seriously think of a Mac Pro and NVidia SLI fully supported and managed by Snow Leopard." This is just speculation.
It's important to keep in mind that Hybrid SLI support for embedded GPU's does not automatically imply SLI support for multiple discrete GPU's. NVIDIA markets Hybrid SLI as a way of pushing it's chipset business while currently licensing discrete SLI to mainboard manufacturers. Since the Mac Pro will not have an embedded GPU or an Nvidia chipset, the support for Hybrid SLI is of little direct consequence to Mac Pro users.
While Apple could license discrete SLI for it's main-boards in the Mac Pro, I'm not sure there is a lot to be gained by it. I suppose OpenCL could benefit significantly, however, gaming on the Mac leaves a lot to be desired... SLI support is the least of the problems. In fact, ask anyone that's owned an SLI gaming rig running Windows and they will likely say they would never do it again. That's certainly how I feel. Nvidia's drivers are flaky as hell and when you add SLI to the mix, it's a disaster.
OSX users should not be too eager to inherit the mess that graphics has become on the Windows platform. Graphics drivers and API's have been nothing but headaches for Microsoft and users of Windows. I wouldn't wish any of it on OSX users and it's in large part why I'm defecting from Windows. Stability is king and Apple tightly controlling all aspects of the OS and system are the only way's to maintain that. Be careful what you wish for.
System Profiler shows tethered. when I remove the SLI cable between the two 8800 gt's I get less graphics performance. I know that the sli cable makes the diff. I understand all the issues windows has. But my two 8800 gt's with SLI cable and Winders vista ultimate 64 games run better than they do on my other mac pro running a single 8800. I understand the info you gave me on the link about SLI 10.5.6. Thank you for your reply.