The Inquirer takes a look at why the Conroe XE's clockspeed is lower than expected:
Another possibility is that Intel is leading AMD on. AMD is now feverishly trying to extract the last drop of juice from its aging 90nm process, and I do believe that 3.2GHz AM2 dual-core parts at near 100 W power envelope are their goal in the next two quarters, just in case 65nm doesn't roll out for them too well. Now, if Intel only announced the 2.66GHz Conroe and 2.93GHz Conroe XE in July, AMD might have less sense of urgency to fight, as the competitive benefit on Conroe side may not be that much then.
Then, after AMD has exhausted its 3Q / early-4Q fine-tuning potential, and depending on its degree of success in getting the first 65nm parts out of the door, Intel might try to deliver a big blow by announcing much faster Conroes (and possibly Woodcrests) by that time. Additional testing and open-market feedback Intel gets by that time might convince it to actually up the frequency quite a bit, well beyond 3.33GHz in that case.