Introduction to the G4
The G4 Processor
Apple's New Big Gun
Two weeks ago, at the Seybold publishing conference, Apple's consistently flamboyant "Interim CEO" Steve Jobs unveiled Apple's latest weapon in its perennial comeback battle: the G4 PowerPC. Jobs hailed the clear and gray system as a "Desktop Supercomputer" and demonstrated applications running 2-4 times faster on it than a 600Mhz Pentium-III. Mac aficionados around the globe hailed this system as the final nail in the PCs coffin, while most PC users yawned and turned back to their daily homage to Bill Gates and John Carmack. In this article, we're going to explain what's inside the G4's powerful CPU, and analyze what's backing up the hype, and what's not.
The CPU in the Apple G4 is officially named the Motorola PowerPC 7400. Since the announcement of the Apple G4 system, the processor has also been referred to with the G4 moniker. Job's Seybold keynote, as well as Apple's TV commercial campaign is heavy with the term "supercomputer" in describing the G4 processor. This claim stems from the performance of the 7400's AltiVec Instruction Unit, also colorfully dubbed the "Velocity Engine" by Apple's marketing department. AltiVec is a set of 162 Single-Instruction-Multiple-Data (SIMD) instructions that are aimed at accelerating mathematical vector functions. In theory, the G4 can do over one billion floating point operations per second (a gigaFLOP), which, according to US export policy, puts the G4 in the realm of supercomputers that cannot be exported to certain countries like China or Iran.
The G4 System with Flatscreen
While 1 gigaFLOP is a great deal of speed for a desktop computer, it is not a very high bar compared to modern supercomputer performance. Remember that the same US export policy that calls the G4 a supercomputer tells us that any encryption stronger than 40-bits is a threat to national security. Another thing to keep in mind is that the performance of the AltiVec unit is a very different thing than standard floating point performance, which is not reflected by the 1 gigaFLOP number.
Still, a billion operations a second is pretty impressive. How does the G4 attain this performance? Turn the page and see.