As we reported previously, the forthcoming 2009 Mac Pro lineup will be based around powerful new technology from Intel code-named Nehalem; better known through great public anticipation in the lead-up to its release as “Core i7.”

We reported on a mid-stream prototype, placed inside an existing-generation “cheesegrater” tower enclosure, in that article which was built on early desktop Nehalem reference board chips including a pair of quad-core, 2.93GHz Core i7 desktop CPUs.

Since then, we’ve had the opportunity to look under the hood of far more recent prototypes and a much clearer picture of the final Mac Pro has begun to emerge.

One of the first questions readers asked after the initial article was posted was whether the Nehalem Mac Pro will employ those standard desktop CPUs which currently tap out just below 3GHz and have been on the market for a few weeks now….or if it will sport Xeon-class i7 chips that offer higher clock rates, more cores, and numerous other advantages over their standard desktop cousins.

Although that detail had been embargoed by our sources at the time and we had not yet actually seen with our own eyes such a machine….

….we were able to confirm last week in web comments & conversations on Twitter, AIM, et cetera that yes, in fact the new Mac Pro would continue to be based around Xeons.

That fact alone means that the Mac Pro will be a significantly different machine than it might have been otherwise.

And whatever else it might have been….the Pro that we’ve had the opportunity to examine is three things for damn sure: extremely sexy, extremely energy-efficient, and extremely fast.