Motorola PowerPC 7400

Historia

The fourth generation of PowerPC processors, the PPC G4, is used in Apple Macintosh computers such as the G4 PowerBook, the 2nd generation Flat Panel iMac, the eMac, the 3rd generation iBook, and the desktop G4 Power Mac. Most of the G4 design was done by Motorola in close cooperation with Apple. IBM, the third member of the AIM alliance, chose not to participate in the design of the G4 in part owing to microprocessor design disagreements concerning a Vector Processing Unit on the chip. Ultimately, the G4 architecture design contained a 128-bit vector processing unit called AltiVec. With the AltiVec unit, the G4 microprocessor can do four-way single precision floating point math, or 16-way byte math in a single cycle. Furthermore, the vector processing unit on the G4 is superscalar, and can do two vector operations at the same time. Compared to Intels x86 microprocessors at the time, this feature offered a substantial performance boost, if the application was coded to take advantage of the AltiVec unit.