> AFAIK there are Powermac G4 cards at 2 GHz available...

"When it comes to 3rd party add-ons it's very unlikely they will be supported from the beginning, or even at all (unless some 3rd party does the drivers). This includes the add-on CPU cards."
https://morph.zone/modules/newbb_plus/viewtopic.php?topic_id=6990&forum=11#71891