Mac OS 10.5 64-bit Impresses

We've been wondering how much performance benefit there might be for 64-bit software on the desktop ever since AMD started talking about the Sledgehammer series of chips nearly a decade ago.  Now that 64-bit is here, in various forms of implementation, we're getting our answers.  Some of the most interesting answers might come from recent tests that "the rest of us" might be curious about.  OS X's latest build has 64-bit support without losing its 32-bit compatibility, and a very interesting performance trend emerges:

“...The performance difference between the 2.8GHz and 3.2GHz Mac Pro isn’t as great as the difference between running 32-bit code and 64-bit code. In fact, the 2.8GHz Mac Pro running 64-bit code is faster than the 3.2GHz Mac Pro running 32-bit code!”

A nearly 15% deficit in clock speeds aside, the 2.8GHz running 64-bit actually manages leads of up to 10% in many tests.  We're wondering if/when Microsoft might finally merge their 32- and 64-bit variants of Windows in the same manner.
Tags:  Mac OS, Mac, Pre, 64-bit, OS, SSE, ses, AC, IM