How does a Phenom II x6 apply its cores to a program?

its just like any other multi-core cpu

Also they only tubro-core 3 of the cores, if a 4th core gets used they all drop to non-turbo speed. This can be overcome with a simple overclock though.

That is not how it works. You can assign a program which core or cores it will use, but you cannot force it to use more cores than the program was written to use. If the program was written to use 1 core, it will only ever use 1 core. It is in the programming of the software/application/program you are using how many cores it will use.

Turbo Core is meant to give you more headroom for ocing which would be otherwise very difficult to reach . e.g: my board is an old AM2+ with 4+1 power phase which is not ideal for ocing x6 cpu, But I can safely oc my 1090t to 3.6 and use Turbo Core to boost it up to 3.8, without pushing the board to its limits.