¿En qué se diferencian un Core Duo y un Core 2 Duo?

Intel Core Duo (product code 80539) consists of two cores on one die, a 2 MiB L2 cache shared by both cores, and an arbiter bus that controls both L2 cache and FSB access. Upcoming steppings of Core Duo processors will also include the ability to disable one core to conserve power.

Intel Core Solo (product code 80538) uses the same two-core die as the Core Duo, but features only one active core. This allows Intel to sell dies that have a manufacturing defect in one but not both of the cores. Depending on demand, Intel may also simply disable one of the cores to sell the chip at the Core Solo price -- this requires less effort than launching and maintaining a separate line of CPUs that physically only have one core. Intel used the same strategy previously with the 486 CPU in which early 486SX CPUs were in fact manufactured as 486DX CPUs but the FPU failed quality control and the connection was physically severed.

Unlike the Intel Core, Intel Core 2 is a 64-bit processor, supporting EM64T.
Other than another bump in the processor speed, one of the primary differences between the original Core Duo and the new Core 2 Duo is an increase in the amount of Level 2 cache. The new Core 2 Duo has doubled the amount of on-board cache to 4 MiB. Both chips have a 65 nm process technology architecture and support a 667-1066 MHz front-side-bus (FSB).

Me engancho por acá porque creo que la pregunta es sencilla.

En una típica conversación de sobremesa en el estudio surgió la duda:
Un Core 2 Duo de 2,4 por ejemplo.
1/ Son 2 núcleos que trabajan a 1,2 cada uno o que juntos llegan a esa velocidad (2,4)
2/ Son 2  núcleos que trabajan a 2,4 cada uno

Gracias

No, es como la 2da opción, cada núcleo funciona a la frecuencia del CPU.
Lo que si comparten los ciclos (hz) de cada núcleo, son los threads que están corriendo en cada núcleo.

http://en.wikipedia.org/wiki/Multi-core_processor

Segunda opcion es ambos nucleos funcionando a la velocidad especificada.

Si se fijan en las nuevas tecnologicas hablan de overclockeo a la volada, cuando una aplicaciones no banca el uso en multicpu, el mismo cpu hace un overclock momentaneo y permite usar unos Mhz mas durante ese proceso, por ejemplo un Core i5 u otros de esta generacion que fuea de 2.4 puede funciona hasta 2.9Ghz momentaneamente, lo que boostea las performances durante un tiempo X.