I am no expert, but isn't 64 bit addressing only a more robust memory allocation system. I mean it allows for larger chunks of memory to be addressed also allowing for bigger allotting of ram on a given system. But the OS and the software have to be rewritten from starch to be able to take advantage of it. As far as I understand it Windows is not capable of 64 bit addressing. OS X is only partially enabled so what advantage would one get if the software simply is not there yet on having this capability. I know that Photoshop has certain areas that have been brought to take advantage when used on G5 systems, but by far not the entire application has this capability yet. I think 64 bit will come to it's own once the operating systems can handle it and once enough developers have embraced it, but know it seems premature to have a system with 64 bit addressing. Now that may change it the next 6 months to a year.