Power Mac G4

The Power Mac G4 debuted in late 1999 and was the first desktop computer to be dubbed a supercomputer, as the PowerPC G4 processor was capable of doing more than a billion floating-point calculations per second (gigaflop). This Macintosh series was superseded by the Power Mac G5 and discontinued in the Summer of 2004.

Models

 * "Graphite" — The first "graphite" version came in two variants: an early "Yikes!" PCI-only logic board that was based on the pre-existing "blue & white" Power Mac G3, while a more advanced "Sawtooth" logic board introduced AGP graphics. Updates later added gigabit ethernet, digital audio, and Apple's new rewritable DVD "SuperDrive".
 * "Cube" — This short-lived version reduced the volume in a 7-inch cube and boasted 3.5 gigaflops performance.
 * "Quicksilver" — This version upgraded specs and simplified the case design into a cleaner look.
 * "Mirror Drive Doors" ("MDD") — This version incorporated the DDR architecture of the Xserve, but heat and fan noise issues led it to being referred to as the "wind tunnel"

Export limitations
For about a year after its late 1999 debut, the Power Mac G4 could not be marketed in the mainland of the People's Republic of China, as the U.S. government deemed the "supercomputer" a "weapon". Apple's interim CEO Steve Jobs used the publicity to market the computers elsewhere while lobbying to have the restrictions removed. Mainland Chinese users were able to get their hands on a Power Mac G4 after this limitation was removed. When the Titanium PowerBook G4 -- the first "portable supercomputer" -- was released, no similar sanctions were in place.