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When evaluating Linux as a possible OS candidate, it is important to remember that the Linux "model" for mobile devices is horizontal. That is, Linux is not presented as a vertically integrated top to bottom solution for a mobile device supplied by one vendor.
It's a sharp contrast to the other OS suppliers such as Microsoft with Windows Mobile, Symbian and PalmSource. These suppliers support a highly integrated software stack, incorporating not only an OS but also extensive middleware and application layer pieces. Arguably the price for such integration is lack of flexibility and loss of control.
Those that have developed Linux-based devices, in contrast, have chosen a horizontal approach, and have filled in the middleware and application pieces by internal development.
They have also turned to the ever increasing Independent Software Vendor (ISV) community that surrounds Linux for mobile devices.
The horizontal approach offers the freedom to differentiate throughout the software stack while adding the functionality necessary to address the unique needs of the market. As a result, commoditization is prevented and the differentiation needed to address unique operator requirements is enabled.
The alteration from a vertical to a horizontal focused approach is not new. Recall that before PCs became mainstream there were vertically integrated word processing machines, dedicated engineering workstations and so on.
The PC, as a horizontal platform upon which application software made the machine a word processor or engineering workstation, forever changed the industry. Although the mobile device market is far from transforming itself in a similar manner as the PC, it has begun the journey with Linux.
Strong Linux ecosystem
The rapid evolution of Linux from to one of the top mobile device OSs didn't happen miraculously. Millions of dollars have been invested into technology and engineering development by major semiconductors including Texas Instruments, Intel, and Freescale, embedded Linux suppliers such as MontaVista Software, and even the device manufacturers.
Additionally, the Linux community (composed of both commercial and private interests) embraced, enhanced and in many cases mainstreamed the additional Linux capabilities. A highly integrated and rapidly moving ecosystem has developed among all the interested parties to ensure that Linux would evolve continuously to meet both current and future requirements for mobile devices.
The result is a mainstream enhancement to the core Linux kernel and its associated software environment, both run-time pieces as well as development tools, that make Linux a competitive alternative, and the OS of choice for some, and a state-of-the-art OS for mobile devices.
Linux emergence enabled by Moore's Law
Underlying the rise of Linux as a serious mobile device OS alternative is the very same phenomenon that had driven the desktop technology for years: Moore's Law.
Moore's Law is the empirical observation, made in 1965 by Gordon Moore, one of the founders of Intel, that the number of transistors on an integrated circuit for a minimum component cost doubles every 24 months.
While we have all seen the effect on our desktop PCs, Moore's Law applies no less to the semiconductor devices used in mobile devices. Coupled with advances in low power processors, by about 2003 it became clear that a mobile phone could be built that was at least theoretically capable of running Linux, from processor functionality (e.g. having an MMU and a large address space) as well as from execution speed (200-300 MHz).
The question was whether Linux could be "trimmed" or engineered to meet the other constraints of the underlying hardware, including operation in a requirement heavy "embedded environment" and memory footprint reduction.
Linux requirements for RAM, if excessive, would be prohibitively costly. Fortunately, Moore's Law, when combined with the industry-driven technology push to make Linux a suitable embedded OS, laid the foundation for its expansion into mobile devices.
In particular, the following gaps between server Linux and the requirements of Linux on a mobile device were bridged:
- Mobile-targeted processors are often completely new silicon so no support for the chips exists in the Linux source trees, requiring a port of Linux to the architecture.
- Removal of Linux dependencies on RAM execution and reduce overall Linux RAM consumption.
- The availability of cross development environments and associated tools since the device itself would not be a suitable development platform.
- Development of Linux-based "simulators" usually a spare PC with Linux since the hardware was under concurrent development with the software.
- The availability of commercial quality, stabilized releases and support infrastructure along with a close working relationship with semiconductor makers to support the new silicon.
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