The PowerBook G4 runs on the RISC-based PowerPC G4 processor, designed by the AIM (Apple/IBM/Motorola) development alliance and initially produced by Motorola. It was built later by Freescale, after Motorola spun off its semiconductor business under that name in 2004. The PowerBook G4 has two different designs: one enclosed in a titanium body with a translucent black keyboard and a 15-inch screen; and another in an aluminum body with an aluminum-colored keyboard, in 12-inch, 15-inch, and 17-inch sizes.
Between 2001 and 2003, Apple produced the titanium PowerBook G4; between 2003 and 2006, the aluminum models were produced. Both models were hailed for their modern design, long battery life, and processing power. When the aluminum PowerBook G4s were first released in January 2003, 12-inch and 17-inch models were introduced first, while the 15-inch model retained the titanium body until September 2003, when a new aluminum 15-inch PowerBook was released. The aluminum 15-inch model also includes a FireWire 800 port, which had been included with the 17-inch model since its debut nine months earlier.
The PowerBook G4 is the last generation of the PowerBook series, and was succeeded by the Intel-powered MacBook Pro line in the first half of 2006. The latest version of OS X that any PowerBook G4 can run is Mac OS X Leopard, released in 2007. When Apple switched to Intel x86 processors in 2006, the PowerBook G4's form and aluminum chassis were retained for the MacBook Pro.