And here it is, the Athlon64. It shares the package with the pricier Athlon64 FX, which has even more pins on the bottom (940 instead of 754). The reason is its memory interface, which can support two DDR channels at the same time. But since AMD is still targeting the workstation market with the FX, only what are known as registered DIMMs can be used; these boost the signals to the chips when needed. For that reason, though, it is not currently possible to adjust the clock speed required for Cool & Quiet. So that's one feature that the high end version can't boast for now.
The "normal" Athlon64 could prove superior to the FX in practice on one score: overclocking. Where the FX has to run two memory channels reliably, the Athlon64 only has to run one. From that you might infer that it can still in all likelihood do that at a high clock speed. The next few months will show if that pans out in reality.
Be that as it may, the current top of the line model, the Athlon64 3200+, features 2.0 GHz. Considering that the Athlon64 FX51 works with 2.2 GHz and that we expect the production process to be practically identical, the Athlon64 should have no problem matching it with the clock rate of the FX.