So, as described in my last project log, I changed the relay of clock 0 (which looked a little bit bouncing). Thats the result with the oszi:

The signal looks much better than before. And the CPU was running with this speed (14,6 ms compared to 27 ms) for minutes without crashing. No, thats not a proof that the clock 0 signal quality was THE reason of the crashes with higher speed, but the bad signal quality before was possibly A reason...

And after that success I wanted to know how fast the system now is able to run. That was the result:

The system was running very stable with a very high clock speed, clock 0 was down to 10 ms...the next two pictures show you the logic analyzer pictures:

First an overview, the measure time is 33 sec, but the system was running for a longer period:

And a detailed view:

Maybe I reached a stable situation and the system timing and the memory software is...not perfect yet, but OK.