It is worse than that. You have Pentium dual core, Pentium Core2Duo (one word), and Pentium Dual Core.
Model numbers are very important.
To make it even worse, there are model numbers that were used in two generations of chips:
Core2Duo E6600 Conroe - 2.4 GHz (266 MHz X 9), 4 MB cache, 65 nm architecture
Dual Core E6600 Wolfdale - 3.06 GHz (266 MHz X11.5), 2 MB cache, 45 nm architecture.