Here is what my friend Google found for me on this topic, at the following address:
AnandTech: Intel's Core 2 Extreme & Core 2 Duo: The Empire Strikes Back
This is not exactly for the 2.4 / 2.8 GHz processors, and the article is dated " July 14th, 2006" but I guess this is still accurate:
AnandTech: Intel's Core 2 Extreme & Core 2 Duo: The Empire Strikes Back
This is not exactly for the 2.4 / 2.8 GHz processors, and the article is dated " July 14th, 2006" but I guess this is still accurate: