The extra registers don't make that much of a difference, since most of the bottle neck has already been removed from them with the advent of register renaming. If you are expecting >0% improvement in *all* 32-bit apps, and >>0% in 64-bit apps, you are going to be in for a huge disappointment.
Sorry, but the extra registers make a huge difference, even with seemingly mundane code.
Maybe my last post will change your mind (the one with benchmarks I ran myself), but I doubt it as you'll site only a limited test. I posted this because it confirms all the other findings I have come up with recompiling other applications for x86_64. I can't post these here as they are proprietary, but I know I'm not going to be in for a huge disappointment. I'm using AMD64 systems today, with great success, and I haven't even hit on using the 64-bit capability. My current set of apps only benefit from the extra registers.
I'll say it again. I think the Windows x86_64 port is going to show a marked improvement in performance over today's 32-bit version, even without recompiling your application. The O/S benefits enough from x86_64 enhancements that it will even speed up 32-bit apps running under it. My reasoning that Windows will benefit more is that the Windows system makes up a great proportion of an application than Linux.
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