Depends on the application of course.
But the difference should be only marginally.
Little bit more info would be helpfull as well.
This is a theoretical question :-) I don't have an application.
Does the CPU emulate 32-bit environment for 32-bit OS more efficiently than
64-bit OS emulate compatibility mode for the same 32-bit app ?
You say, that the efficiency that I'm speaking of (above, in the quote) can only be measured by special test-case application?
Let's say that I'm speaking of SUN JVM 1.6.0 32-bit, the linux version
Just in case it's helpful, AMD has Athlon specific forums: http://forums.amd.com/forum/index.cfm?FTVAR_SUBCAT=20&nocookies=y&subcatname=Desktop%20Products%20%28Phenom%E2%84%A2%2C%20Athlon%2064%2C%20Athlon%20XP%20%26amp%3B%20Sempron%29