Office 2010 and 2011 : 64-bit version not recommended (or impossible to install)
June 09th, 2010 - 10:15 am ET by J. G.
The future Office for Mac engine will only be available as a 32 bit version. The 64 bit version of Office 2010, which is available, is not recommended by Microsoft.
While Microsoft Office 2010 will be available in both the 32 and 64 bit versions for the first time on Windows, it won’t be available on Mac OS X. Planned for release at the end of the year, Office 2011 for Mac will only be available as a 32-bit version.
Jake Hoelter, Product Unit Manager / MacBU, reminded users that Office 2011 will use some Apple technologies like Cocoa. This is notably the case for Outlook which will take over from Entourage, with the program developed in Cocoa, while other new user interface elements like Ruban will be seen. This should allow for Office 2011 to be well integrated into the Mac environment.
Jake Hoelter also indicated that the transition of the user interface through Cocoa isn’t yet complete, which has prevented the release of a 64 bit version. "The Apple framework requires that we complete the transition to Cocoa before being able to offer a 64 bit version".
Getting over the Cocoa obstacle This issue isn’t considered as overly grave by Microsoft, in the measure that the real advantage of their 64 bit version was that it could treat large quantities of data, with an Excel example being that "data in millions of cells" could be worked on (a file of 2 GB for example). For common users, the performance difference between the 32 and 64 bit versions is little.
A very similar reason was offered up by the Windows Office Engineering team to explain the differences between Office 2010 32-bit and 64-bit versions, although more of an emphasis was put on compatibility issues with existing Office extensions. Between Windows 32 and 64-bit versions, Microsoft recommends Office 2010 in the 32-bit version, considering that the "64 bit ecosystem for Office is not yet sufficiently mature".