There is no way to turbo boost from 2.53GHz to 2.66GHz only by software configuration, are you sure?
As
@GMShadow said, Core 2-series chips were released before Turbo Boost was even released. Only Core i-series chips have them.
What the article means is:
This model comes standard with a Core 2 Duo P8700, however for an extra $150 at the time, you could upgrade it to a C2D P8800, which has a higher clockspeed.
This is the same as ordering a new phone with 64GB of storage or 128GB of storage, or configuring a new Mac with 16GB of RAM or 32GB of RAM.