You’re getting into a tricky area here. Until the 64-bit version arrives the 32-bit version of Revit should have no problem running on an x64 system, provided all the required drivers are available in their 64-bit iterations. Most 32-bit software will run quite happily on x64 via the emulation layer built in to the x64 OS. Do a search for “Wow64” for some background on how this works. Basically this layer translates the 32-bit instructions from the software into 64-bit instructions to the OS; the program (Revit) thinks it’s in a 32-bit environment. The implication of this is that as a result the program will not take advantage of the 64-bit address spaces and registers (translation: 64-bit performance), nor will a 32-bit thread operate outside the 2gb memory limit. However, programs written to take advantage of the 3gb memory switch are supposed to get a full 4gb of memory space in the x64 environment, but there’s still terribly little data on (if any) performance gains with Revit 08.
All of this also depends on whether your x64 system has more than 4gb of RAM installed.
