TRNG by hamming distance of processor tics I hardly remember on a lecture, where it was told, that the distance of the practical actual running-speed of a processor to the previous tic is used, to generated a true random entropy for seeding. But I cannot find any source for proving this memory right. 

So my question arises: Is this a way to generate a true random seed and spawn so a trng?
You are talking about using the relative jitter of 2 timers to source entropy.

That is indeed an option for entropy generation. 

However in terms of cryptographically secure RNGs (the reason you would go to such length to create randomness) this jitter can be influenced by the load on the processor and electrical noise. This provides a side channel to try and influence or predict the entropy used for the generator.