Will a hexa-core give much more increase in clockspeed on active cores, for example 2 cores is in use, when hypertransport is activated than a quad-core? Thinking about the Phenom II x4 960T @ 3.3GHz and Phenom II x6 @ 2.6 GHz with 2 active cores and activated HT.
Hypertransport is what AMD uses as a communication link between the ram and CPU. It was created to replace the FSB for this and has nothing to do with clockspeed. AMD CPUs do not increase their clock speed based on workload past the maximum rated speed. This is what intel does with their turbo on their CPUs.
There is speculation that AMD may include a similar feature in their upcoming Thuban 6 core processors but nothing has been confirmed, nor have there been any more details on how they will do this. Again, this has nothing to do with hypertransport. This is also future technology so it is unknown what speed increase is expected if they are implementing this technology at all.
I'm not sure but I believe my last paragraph answers your question. If it doesn't, please let me know and clarify what you are asking.