Hi Gerardo,
thank you for the warning and sharing your experience with us.

I'm not surprised too... It's nearly impossible to find WDC CPU rated 8 or 10 MHz. And as you already mentioned 14 MHz CPU W65C02S6TPG-14 doesn't work as an replacement in all of our chess computers...

But in some it does Possibly we can collect helpful infos on this topic. For Polgar it works, for MM IV and V also. For MC IV LE I was not able to get it run with correct display. I think it could be a timing problem.

Cheers,
Andreas