interview with AMD’s Dr. Raghuram Tupuri
 

We often hear the comment that there is no point in investing in 64-bit processor configurations before more applications become available at 64-bit; that without 64-bit apps there will be no performance gain. What is your response to that dilemma?

As a designer, whenever I hear Opteron discussed only in the context of 64-bit, that hurts me because Opteron is much more than 64-bit. It has so many performance advantages that even if I don’t run a single 64-bit application, I’m still getting full dollar value for Opteron. The Opteron seamlessly delivers performance for 32-bit applications. It has built-in micro-architectural enhancements that optimize performance, whether at 32- or 64-bit.

http://www.digitimes.com/bits_chips/a20051213PR200.html