Having seen that Powerlogix designed a whole iMac system board from scratch, another possiblity just came to my mind...
Would it be possible that Powerlogix invented a G4 add-on card for PCs? It would be the "evil-twin" of the Orange PC card, but run on the AGP port of a PC.
Athlon 1000 + G4 500 dual processor PC: ultimate compatibility and upgradeabilty