Haha, yes, I see.
Thank you for the reply!

I have a lot to read.
Six years ago I had not yet got the new interest for chess computers.
I read the forum threads day after day, trying to learn.

It's actually strange there is not one single active forum thread about the
use of W65C02S6TPG-14 for repair/tuning.

Well... I think it has been discussed somewhere, but I can't remember where!

The truth is that my relationship with this microprocessor is a love/hate one. Thanks to it, and to the North American company that continues developing it (WDC) we have been able to do many repairs, new projects, etc. But on the other hand, the lack of backward compatibility has sometimes driven me crazy, working well on some computers, and badly on others apparently the same. What I can say is that, apart from the changes proposed by the manufacturer itself (read here), many problems derive from the "quality" of the system clock signal:


Best,
Gerardo

Yes , I agree with that too.
That is one of the reasons (e.g. Conchess) the quartz crystals often run at double speed than the CPU - to shape the system clock signal better!