When we last left the PowerPC processor line in Part I of this series, Apple was enjoying the performance and competitiveness that the 600 series of PPC processors brought to the company's flagship PowerMac workstation. Now, in Part II, Apple transitions to the 750 and then the 74xx series, a capable series of processors that are built on the solid fundamentals of their predecessors.




In spite of its short pipeline and small instruction window, the 750 packed quite a punch. It managed to outperform the 604, and it was so successful that a 604-derivative was scrapped in favor of just building on the 750. The 750 and its immediate successors, all of which went under the name of "G3," eventually found widespread use both in the embedded arena and across Apple's entire product line, from its portables to its workstations.



The G3 lacked one important feature that separated it from the x86 competition, though: vector computing capabilities. While comparable PC processors supported SIMD in the form of Intel's and AMD's vector extensions to the x86 instruction set, the G3 was stuck in the world of scalar computing. So when Motorola decided to develop the G3 into an even more capable embedded and media workstation chip, this lack was the first thing they addressed.




Of course, as we all know, in spite of good processor designs and excellent performance/Watt ratios, Apple began to lose performance ground to the x86 world during shortly after the rise of the 750. The present article doesn't get too much into playing the blame game for why the PowerPC line ran out of gas during the period covered (*cough* MHz *cough*), though I do say a few words about it. The main focus, however, is on the architectures of the chips themselves, and what made them stand out from each other and from their competitors.


http://arstechnica.com/articles/paedia/cpu/ppc-2.ars