Eh, these things tend to move in cycles. ARM, for instance, was Acorn's desktop architecture, then Acorn's desktop line died off and it found its bread and butter in embedded applications for many years, then it started popping up in handheld devices (GBA, iPhone and now just about every smartphone,) and all of a sudden it's popular again and possibly on the verge of breaking back into the (low-end) desktop market. PPC has already gone from desktop to embedded to game consoles, who's to say it won't make a similar comeback?
It's not "a cycle thing".
ARM's design allow low power consumption and cool computing. That was an enabler for mobile devices, an area which has had a tremendous growth. That, coupled with ARM's license based business model that allows companies to combine ARM's core design with other controllers to make their own CPU chips, is what really makes the opportunity. Look at Apple (with iPhone and iPad - all ARM!) and the Tegra based devices (and most other mobile devices as well). The future ARM designs scales heavily upwards in performance, while still being low Watt and low temp, and nVidia (and probably others as well) will really create a big bang when they release the really high performance stuff. Rumors has it that Apple has an ARM based laptop coming soon. Windows 8 (and Office, etc) will be ARM. It will boom, it will cover everything to the tiniest, most ultra mobile device, up to the fattest workstation and servers, and it will be the same ISA.
http://blogs.nvidia.com/2011/01/project-denver-processor-to-usher-in-new-era-of-computing/nVidia: "Denver frees PCs, workstations and servers from the hegemony and inefficiency of the x86 architecture. For several years, makers of high-end computing platforms have had no choice about instruction-set architecture. The only option was the x86 instruction set with variable-length instructions, a small register set, and other features that interfered with modern compiler optimizations, required a larger area for instruction decoding, and substantially reduced energy efficiency.
Denver provides a choice. System builders can now choose a high-performance processor based on a RISC instruction set with modern features such as fixed-width instructions, predication, and a large general register file. These features enable advanced compiler techniques and simplify implementation, ultimately leading to higher performance and a more energy-efficient processor.
Microsoft’s announcement that it is bringing Windows to ultra-low power processors like ARM-based CPUs provides the final ingredient needed to enable ARM-based PCs based on Denver. Along with software stacks based on Android, Symbian, and iOS, Windows for ultra-low power processors demonstrates the huge momentum behind low-power solutions that will ultimately propel the ARM architecture to dominance."But that's "Denver", a future thing - But do you want to see "Windows 8" (development version of Windows) running on
*current* ARM-technology?
Well, Fast Forward to 1.10:
[youtube]lRPh4kJpeSA[/youtube]
I'm sorry, but I don't see remotely the same momentum happening on the PPC platform.
Apple was the last one who left. Now it's all about routers and automotive. Which is a huge market as well, but hardly very interesting to us...