mk79 wrote:OK, I'll solve :-) It was quite obvious when you have the QL in front of you but almost impossible to guess when not... though Tobias analysis came close with problems in the upper area.
Anyway, I forgot to remove the internal QL-SD before plugging the external one in. So there were two ROMs running at the same time! The twist is that one ROM was a German Minerva and one ROM was an English Minerva. These are in large parts identical as the language specific part is towards the end... so they agreed enough on the code to make it run flawlessly, but when they tried to access anything language specific they strongly disagreed and the result was garbage on the data bus :-) Still, thought this effect was interesting enough to share.