I just destroyed my seccond iBook G4 12" mainboard of unfamiliar reasons :'(, and I might get a PB G4-mainboard for a nice price. Anybody knows wether it will fit at all or other issues that might occur?
The short answer is no. All of the screw mounts, heat sink assembly, and internal build dimensions are diffrent. The ports wont line up either. Likewise, the screen, power, optical drive and battery hookups are differentl Lastly, the dc-in board is different. It would actually be easier to paint a powerbook white, than try to shoe-horn it into an ibook enclosure.
Of course, not that I'm trying to kill your idea entirely. Just giving you a straight answer.
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Electricity tastes good. No, seriously.