PowerPC G4

The PowerPC G4 (74xx) is a brand name that was used by Apple Computer for 4th generation microprocessors from the PowerPC line that were developed by the AIM alliance, which included Apple, IBM, and Motorola. The G4 processors were marketed as powering the first "desktop supercomputers", which included the Power Mac G4 (and G4 Cube), PowerBook G4, iMac G4, iBook G4, and eMac.

Features
G4 processors contained a 32 KB instruction cache, a 32 KB data cache, and varying levels of support for L2 and/or L3 caches. They were touted by Apple for containing a "Velocity Engine", a 128-bit vector processing unit marketed as AltiVec by Motorola, and Vector Multimedia Extension (VMX) by IBM. Though the IBM and Motorola versions use compatible instruction sets, the hardware logic implementations are very different from one another. The PowerPC G4 also introduced a high-speed system bus known as MPX, which more than doubled memory bandwidth. MPX was supported by almost all Power Macintosh G4 models, except the first entry level configuration, known as "Yikes!".

Processors

 * PowerPC 7400 — code named "Max", supports up to 2MB L2 cache and used in the first "graphite" Power Mac G4 models between 350 to 500 MHz.
 * PowerPC 7410 — code named "Nitro", a low power version with support for up to 1MB L2 cache, used in the first Titanium PowerBook G4 models between 400 to 500 MHz. Pin compatible with latter PowerPC G3 processors, making possible upgrades of PowerBook G3 "Pismo" models.
 * PowerPC 7440 — code named "V'ger" and sometimes called "G4 Plus", operated at 1.5V and contained 256KB onboard L2 cache, but did not contain L3 cache support. Used in Titanium PowerBook G4 models with gigabit ethernet.
 * PowerPC 7450 — operated at 2.5V with 256KB onboard L2 cache and also supported an external L3 cache. Used in Power Mac G4 models between 667 to 800 MHz.
 * PowerPC 7441 — code named "Goldfish", a minor "errata" update with nearly identical specs as the 7440. Used in 700 MHz eMac and iMac G4 models.
 * PowerPC 7451 — a minor "errata" update of the 7450 with external L3 cache support. Used in the Titanium PowerBook G4 models with DVI video.
 * PowerPC 7445 — code named "Apollo 6", used in iMac G4 models between 800 MHz to 1.25 GHz.
 * PowerPC 7455 — supported an external L3 cache. Used in the Titanium PowerBook G4 models between 867 MHz to 1 GHz.
 * PowerPC 7447 — code named "Apollo 7", contained 512KB onboard L2 cache, but did not contain L3 cache support. A revised 7447A was used in the last 1.67 GHz Aluminum PowerBook G4 models.
 * PowerPC 7457 — operated at 1.1 to 1.3V with 512KB onboard L2 cache and also supported an external L3 cache. A drop-in replacement for any 7455 running at the same voltage. Used in some iBook G4 models.
 * PowerPC 7448 — code named "Apollo 8", contained 1MB onboard L2 cache, but did not contain L3 cache support. Only used in third-party accelerator boards. There are discredited rumors that Apple used a 7458 (which doesn't exist) in some of the last PowerBook G4 models.

Marketing
The United States government banned export of PowerPC G4-based computers to over 50 countries due to its status as a supercomputer. Apple's interim CEO Steve Jobs used the publicity to market the computers while lobbying to have the restrictions removed.