In my travels I run into lots of people who are running Microsoft Office 2010 but many of them are also running the 64 bit version. I thought I’d do a quick post to discourage this behaviour!

Yes, we’ve had it drilled into us that 64 bit is the future, and, for operating system installs you do indeed want to be running Windows x64 because you’ve probably got more than 4GB of RAM in your machine. However, when it comes to applications that have been specifically compiled for 64 bit I suggest a much greater degree of caution and reflection before diving in. It is basically a trade-off by way of sacrificing raw performance for the ability to use more RAM in that application process. What do I mean by this; Well, there is an overhead in working with 64 bit pointers and this will mean that you take a performance hit in running the 64 bit application- see this article for some simple benchmarks http://www.osnews.com/story/5768. The flip side, however,is that you can then work with a full 64 bit address space and thus your application can use more than 4GB(ish) of RAM.

So, why do I want to discourage you from installing 64 bit office?  

1. You probably don’t need that much RAM for a individual Office application.
   Unless you are working with extremely large spread sheets in Microsoft Excel it is unlikely you’ll need to use > a couple of GB of ram for a single Office App.
2. There will be a performance hit.
3. There are significant compatibility issues
   If you use Office add-ins and other 3rd party extensions you’ll find that compatibility with x64 Office is patchy at best.

So there you have it. The typical person I se running 64 bit office is the ‘IT Guy’ or enthusiast for whom more bits == more power. This just ain’t the case.

Here is the official Microsoft article on the situation: http://technet.microsoft.com/en-us/library/ee681792.aspx