Alvin Mok notes that Apple has posted the developer notes for the lastest iBooks and PowerBook G4s as well as the Developer Note on OS X 10.1:
"For the iBook, nothing is significant except for the speed pump. For the PowerBook G4, it's entirely new. The 550/667 MHz G4--which model is not stated--should be the PowerPC 7440 since it has a 1:1 built-in 256 KB cache. The Uni-N IC should be the "rev 1.5" used in the PowerMac G4 which supports 133 MHz FSB and AGP 4x graphics. The CardBus chip is new (benefits not stated). The sound chip is also replaced by the Tumbler employed on the PowerMac G4 and iBook which capable of handling 16-bit 48 kHz sound samples. The Gigabit Ethernet, like the one on a PowerMac G4, doesn't require a cross-over cable to hook up two machines."