Apple said that an Intel-based replacement for the 2003's PowerPC-based Power Mac G5 machines had been expected for some time before the Mac Pro was formally announced on August 7, 2006, at the annual Apple Worldwide Developers Conference (WWDC). In June 2005, Apple released the Developer Transition Kit, a prototype Intel Pentium 4-based Mac housed in a Power Mac G5 case, that was temporarily available to developers. The iMac, Mac Mini, MacBook, and MacBook Pro had moved to an Intel-based architecture starting in January 2006, leaving the Power Mac G5 as the only machine in the Mac lineup still based on the PowerPC processor architecture Apple had used since 1994. Apple had dropped the term "Power" from the other machines in their lineup and started using "Pro" on their higher-end laptop offerings. As such, the name "Mac Pro" was widely used before the machine was announced.