PowerPC G3
From Free net encyclopedia
PowerPC G3 is a designation used by Apple Computer to a third generation of PowerPC microprocessors. The term is often, incorrectly, imagined to be a physical model of processor when in fact a number of processors from two different vendors have been used.
The G3 is a RISC-based microprocessor, belonging to the PowerPC family of processors. Such designations were applied to Apple Macintosh computers such as the PowerBook G3, the multicolored iMacs, iBooks and several desktops, including both the Beige and Blue and White Power Macintosh G3s. The low power requirements and small size made the processors ideal for laptops and the name lived out its last days at Apple in the iBook.
The PPC 740 slightly outperformed Pentium IIs while consuming far less power, and being smaller in size. The PPC 750 added an off-die L2 backside cache, which increased performance by approximately 30% in most situations.
Initial models of processor used were manufactured by Motorola namely the PPC 740 and PPC 750 (codenamed Arthur)- both derived from the earlier 603 with the PPC 750 offering an off-die (SRAM) Level 2 backside cache of 512 KB or 1 MB, with the PowerPC 750 outperforming the 740 by about 30% in most situations. These initial models, used in the Beige Power Mac G3, used a copper fabrication process, and topped out at (at least retail) 333 MHz. Later versions used an aluminum fabrication process, and reached 500 MHz, as found in the last of the PowerBook G3s. Later versions were manufactured by IBM, based upon different versions of the PPC750, utilizing a "silicon on insulator" fabrication process, as well as die shrinks, achieving speeds of 1 GHz and beyond.
All models in this generation had issues with the symmetric multiprocessing capability which made design and manufacture of a multi-processor computer comparatively difficult - this was not corrected until the PowerPC G4. The lack of multiprocessing capability and weaker FPU were the only real "downgrades" to a G3 from the previous generation of the PowerPC, the 604e.
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